I just scan the FM portion of 2 meters if I am traveling. I don't much bother with UHF when traveling.

It is not uncommon for the power switch to go bad so I would check that. Mine went recently.
Not certain but I think they are not slo blo fuses and are ceramic fuses instead of glass. If a fuse is blown you can check it with a multimeter to be sure, if it is a glass fuse it should be obvious. If one is blown then there may be a problem with the amp.
I think that Radio Shack has ceramic fuses of that value. I changed my AL-811 to 240V and used glass fuses as I couldn't find ceramic fuses of the right value locally. It had ceramic fuses in it when I got it but it was used.

Another choice is the Autek WM-1 computing wattmeter, a true peak reading wattmeter. It would be my first choice. Only drawback is that they won't give out a schematic for it. They don't want copies of it being made offshore somewhere. It is $160 so pretty close to the price of some non peak reading wattmeters.
If you don't care about the peak reading feature there are a lot of decent wattmeters out there. I used to have a W-4 and it was a good meter. Nice size and the remote sensor is always a good idea.

"that I know about"...therein lies the caveat!
See what you can do to get it to fire up before you make any decisions.
If it was represented to you as a parts rig, you will be real lucky if it does!
Nothing worse than buying a parts rig for a parts rig that ends up as a (you guessed it) parts rig!

If you are getting the HB-1 boom, I wouldn't waste time trying to feed the iCM mic cable through the boom. The Heilwire cable is too thick. I took a chance at it and removed the mic plug. I gave up after about an hour. I couldn't get it past about 3/4 the way through the first piece.
I have two iCM hand mics, and a Proset Plus IC with the iCM element and the H-4, and a BM-10 headset with the H-5 element.
I mostly use the iCM elements. They all have their place and work well.

Velleman makes a signal tracer/injector kit that retails for about $20 and there are a couple other kits as well. They are easy to find in a search.
I have the Velleman. It just needs a small project box to house it in.

Only when the amp is actually in use and not in standby or otherwise bypassed.

So if you used the amp in transmitting, your internal tuner would be looking at the amp input only. If you have it in standby then it looks at whatever is past the amplifier.
If you turn the amp from operate to standby often during a QSO (for whatever reason) your rigs internal tuner would be changing settings each time.

If your amplifier has a tuned input it shouldn't be necessary to have the rig internal tuner on when using it unless as previously mentioned, the tuned input is off a ways on some band.

OS far as I know HRD doesn't lend itself to contest logging very well if at all. More of a general purpose logging program, for chasing awards etc.
Most would use N1MM for contest logging or something else more specific for contest logging and then export in an ADIF file to the general purpose log later on. For casual contesting you can use whatever you want but it may be difficult to keep track of who you have and haven't worked to avoid working "dupes" (duplicate contacts). Also you may not be able to see what your score is or export a Cabrillo file to send your log and score in with if you decided to send in an entry.

Although a contesting log will keep track of the contacts by number 1,2,3,4,5 etc. it is not so much something to "generate" as to keep track of. In a CW contest the software will generate the consecutive serial numbers as you go so it can be sent by keyboard with a macro. In phone contests it will show up as you log so you know what number you are at to send it as part of the exchange
If you receive a serial number from someone either phone or CW, you would log it as part of the received exchange. If you are not sending in a log, logging it doesn't really matter much.

You can also log the "old school" method by hand on a paper log and dupe sheets. Later you can type the info into your computer log.

In general terms, 40 during the day and 75/80 in the evening from my experiences with HF mobile operating. But of course it is nothing you can necessarily count on. There are at least a few variables to account for and the time of year will have an effect too.
I think many in "emcomm" think that HF communications has some certainty to it and it just doesn't.

In the IC-7600 user group some have brought out the spectrum scope to an external monitor but that is all. It is not terribly hard from what I have read but don't think it is worth the effort and only offers limited "eye candy".
Unlike the IC-7000, there is no composite video output with the Pro 3 or 7600. I have not heard of anyone bringing out the entire display and would be surprised if anyone has. The Pro 3 has a non standard display, the 7600 is QVGA while the 7700 and 7800 are VGA and have ports for video output. Also, the Pro3 has 320x240 resolution while the 7700/7800 has 800x400.
I don't think 320x200 would look very pleasant on a large monitor like 800x400 would.
The caveat of course is that someone can really screw up a very good rig trying to do these things if they don't know what they are doing. The risk is their choice of course.
I would join the 756 Pro 3 user group and ask about it there to get a more definitive answer about it.

You only need 30 and there are endorsements for 36, 37, 38, 39 and 40. Not sure why.

DXCC on 2 meters is largely done on EME.
It isn't particularly difficult but putting up decent antennas would be a pain and fairly expensive. You can have a small fortune in N connectors when you are done with some of the larger arrays! A tower doesn't have to be very high though.

WAZ on 5 bands would be tough as you have to cover the whole globe on each band.

When you think about it, one can potentially get DXCC on a band just covering part of the globe.
Something like North and South America, the Caribbean, and some Oceania or western Europe.

Not to mention it can be done in a weekend, sometimes on a single band in a major contest. I worked 84 entities on 20 in the ARRL DX phone contest earlier this month. Not 100 but getting fairly close!

They both have their problems. I have three busted HD-73 rotors in the garage. There is a plate inside that is made of pot metal and it will break at times from lateral torquing. The motor gears are mounted to it. There is no decent brake, just a couple small round cork pieces that collapse on each other to hold the rotor in place after turning. I would only buy a used one for parts unless it has been rebuilt by someone that does it a lot. Two of the three I have were bought at hamfests for parts. They were complete (and known to be broken) with the control boxes and I didn't pay more than $20 for either. One of these days I'll get one running out of the three but it is a very low priority.
A rebuilt Ham 3 (or newer) is a better choice and is what I have been using for years now.
Both myself and a friend had our HD-73's bust with just a Cushcraft A4 to turn. I would not leave an HD-73 all the way south nor approach where it stops when all the way south without creeping up on it slowly. Banging it against the stops probably isn't healthy.

With the mini and junior beams it may not be as much of a problem.

If you really want to keep up on DX activities, subscribe the the Daily DX.
You will miss a lot if you just watch these forums. I am on QRZ.com a lot
and only rarely look at the DX forum. Not a lot of difference between this DX forum and the one on QRZ. DXing is one of my primary interests.

There is a conductive copper paste you can get for that. KLM used to include some with the KT34A.

For my money they are overpriced at $49.95.