The critical value for LEDs is the current. The ones in Wouxon or Baofeng have a limit of 20 mA as regular current. If yours gets bad I'd say a higher value resistance in series should do the trick. Why don't you ask you dealer about that? He could check and increase the value of the existing series resistor.
From the KGUVD1 I know that the LED is switched via a transistor and a 150 Ohm R. May be 180 Ohm works better.

It depends on what output power you have and how well your scanner input is protected. If possible short the input to ground.

I can't point you to a circuit.
Your problem is that a speaker has usually a low impedance but high voltage. Your microphone input requires low voltage. So you can try to just couple the input using a capacitor. If you need to correct the voltage, i.e. if it is to high, you could use a potentiometer to reduce it. Another approach would be inductive coupling using a choke.

I'd check the voltage like every hour. That should give some information.

First thing I'd complain about the missing manual.
If it is similar to the CD-15A then steady red means charging, blinking red charging soon complete. Charging done, steady green.

You didn't mention the antenna you are using. Perhaps you can rotate it and pinpoint a direction. Disconnect your antenna just to make sure it does not come from your rig.
The June issue of QST has an interesting article about RFI.

The first units of the Baofeng radios did not fulfill the FCC requirements. One needs to be careful.

Probably you do not have much measuring equipment like a simple RF meter (GE diode and C) in front of your meter/oscilloscope to check out RF amplitude.
For simplicity I recommend using the NE602 as per the link I mentioned. The L* in that circuit is fairly uncritical, i.e. I changed the length in a wide range and the oscillator always worked.

It took me a while to locate this: http://www.qsl.net/sv1bsx/2m_converter/2m_conv.html
The oscillator of this circuit did not work without the L*. After inserting it, however, it was strong. Good circuit for downconverter.

It does actually not matter what generates the signal as long as frequency and amplitude are what you need.
From own experience I can tell you that xtal oscillators can be hard to get going at frequencies above about 60 MHz because they are 5th overtone. You might try one of those active xtal oscillator circuits.

A bit closer to Malta is http://www.reichelt.de/
I think they would also ship to Malta. They got a good selection of electronic tools at reasonable prices.

This unit does not look bad. Why don't you ask them about using it as planned?

Well, there are lots of circuits to be found searching the web. Probably you can find some in QST as well.
Basically what the circuit should be doing is in a sequence to first ground the RX input, then switch the antenna to the power amp and then power should come on. All that in very short time.
The grounding of that pin could directly switch a relay to ground, the other side permanently connected to positive. However, the relay will not do the job. So you'll need a sequencer circuit, which is triggered by the grounding of the input.
I think, MFJ also offers ready made antenna switching units.

Measuring power should be done with a dummy load, not an antenna. This would exclude any influence on that side.

The ACC connector pin 7 is grounded on transmit, see page 12 of the manual. You can use that to activate the external antenna switch.