135" is a good size screen IMO. I sit 12' back with a 120" 2.35 screen and it's fine for me. It could be a little bigger, but I have no regrets with it.
People who have bars can answer this better, but personally I would not want to watch a movie sitting at a bar. I think it looks cool and would be a great place to hang out, but I don't want to sit on a bar stool for 2 hours watching a movie.
As far as speaker placement you have to work with what you have. Moving a speaker here or there a couple feet is not going to make a dramatic difference.