Tanxalot:

Paint rubbing off: Did you clean the hull first? Good surface preparation is ~essential~. Yes, you may want to strip out many of the mechanicals first... and use something relatively strong, Castrol Superclean or Mean Green (many of us use this as a paint stripper) Then clean it again with a decent brand of dish-washing soap, and rinse with HOT water. A gottle of the Castrol or MeanGreen is mebbe $6. Easy Off oven cleaner is almost the same. Watch out, none of these is kind on the hands, so wear some kitchen gloves, and DON'T use it on aluminum parts. It EATS aluminum!

Bits falling off: Many plastics have different adhesion qualities, but the best glue for styrenes is Tenax-R or a similar liquid solvent product. Get it cheap at a plastic's shop as MEK, and they often have syringe-type dispenser mini-bottles too, so you don't have to find a Touch-n-Flow. Also make sure you're gluing to a ~clean~ surface, by scraping away a bit of paint to put the piece styrene-to-styrene. Neat thing is you can apply this with the pieces already assembled as it 'wicks' into a joint. 500 ml should run you about 10-12 bucks.

Metal tools? I assume ya bought aftermarket... why not make some tie-down straps like the real tanks had. Use loops of wire that go through to the inside of the hull and are net over, then make a 'strap' for the tool from something like thin paper tape. I've seen a guy that sells stuff for making seat belts on eBay, would be good for tool webbing too, I think. Or the germans have webbing, and even PE buckles too.

FV432 said it right on the LED's, but don't grind too much off. The lights probably need a higher voltage. Mask a thin strip in the middle of the LED, paint with black first, then the camo color, and remove the strip-mask. If they don';t light up one way, you got the leads reversed (check before ya solder 'em)

As for item #4, see answer #1.