On LEDs, the amp draw of a good set of bulbs should be less than a single halogen bulb(about 5 amps total). I wouldn't bother with a relay, it's way overkill, and would not actually make them brighter. LEDs run off a driver chip that controls current usage to some extent, so they really are great for our trucks electrical wise. The only issue is that the way they cast light is different from halogen so the pattern is not ideal in a factory housing. And technically illegal in the USA (as are any bulbs on public roads not specifically designed for that housing) but that to me is, well...more guideliney haha.
As for the wipers, I had great luck on one of mine by popping the clockspring cover and fixing/cleaning the contacts. Your symptoms sound like you may be having that issue as well. I didn't even have to pull the motor out. Saved money and work.