1. You can adjust the pass/run sliders for each team. I believe this is done in the coaches menu > strategy section. That being said, I haven't had problems with teams only passing (although I've heard of other people complaining about the same thing). I haven't touched those sliders and the CPU does whatever it can do against me. If I can't stop the pass, they pass. If I can't stop the run, they run. I've had teams have huge days against me by either running the ball or passing.
2. Search for the recruiting info using this forum's search engine. You'll get all the info you need.
3. I'm not sure what you mean by this question. You don't explain why you think you're bad. Is it because you've never returned one for a TD? Is it because you average 1yd per return? If it's because you've never returned one for a TD I wouldn't say it's a bug. I've played a combined 8 seasons (4 seasons with 2 teams) and I've only returned 2.
4. You'll get this info during offseason. The limit is 70 per team. I don't remember the specifics per position.