Your nap time situation sounds so difficult...I'm afraid I don't have any useful suggestions, as my dh (for the most part) works from home, so he could always take the baby when I had to get dd1 down for a nap.
Neither of mine nap anymore, so the whole naptime struggle seems far away to me at the moment!
As for limiting nursing...I started with dd1 by delaying. If she asked to nurse when I was in the middle of doing something, I explained that I needed to finish what I was doing, and then she could nurse. This got tantrums at first, but she quickly learned that if you tantrum for something, you definitely don't get it, and she became more patient.
I didn't really have her wait very long at first...it was just getting the idea that sometimes you needed to wait to nurse, you know?
Then I stopped nursing her in public (probably when she was around 2, I think). I'd just explain that we only nursed at home, so she would need to wait. For the most part, we could stay busy enough when out that she wouldn't ask to nurse...
As she got older, I kind of spaced out her nursings. If she'd just nursed and asked again in 30 minutes, I'd explain that we needed to wait until after 'X' event (lunch, etc.). Just knowing when exactly she could nurse again seemed to help.
I don't really limit my 21 month old, but she isn't a heavy nurser...and she has also learned that sometimes you need to wait. I don't nurse mine at the same time, so that has perhaps helped my girls with learning to wait their turn to nurse?
Hang in there - hope some of that helps. The only advice I have for your nap situation is decidely un-AP - get a swing! The few times dh wasn't around to take dd2 when I need to focus on dd1, the swing was a godsend....
Perhaps bumping this topic up will bring out other posters with great advice.