Cmon man. Saying incline and decline benches are not important is rubbish. Of course you can push a lot of weight on normal benches if thats all you do.Before I educated myself more I did exactly what you're proposing. I got strong as hell doing it, but I also wore myself down. I did way too much too quick. With a proper routine I was able to focus where I needed to and became a more rounded lifter (I made up the previous routine myself cobbled from other things I heard from other routines).
IMO as long as you don't go crazy, and use ideas from established routines, or even just the routine itself and see how it works with you (over months). You will be good to go. There's nothing wrong with changing a routine around to fit yourself.
That said, now that I know what I know, I would not do a bodypart specific day routine again if I could go back in time (maybe I would if I were supplementing with anabolics). I would find a really good established BB routine or a good established Strength routine, or a mix of both. It all depends on your goals.
If you're more into body building try to get in contact with Mecha or Darth in this thread. Those two guys are going to be probably the most knowledgeable about those types of programs. I'm more of a strength guy.
1. Does your personal trainer know you're trying to do Starting Strength? Does he know what it is?
2. Those other benches aren't important. I don't do decline at all and my bench is strong as hell. I will sometimes do incline though, but again, it's not important.
3. Starting strength is a beginner program. 1 set of 5 heavy deadlifts for that day doesn't include the warm up. You should do a few warm up sets before you get to your final set of 1x5. Also, deadlifts are one of the most taxing things you will do (probably the most). At this point 1x5 is all you're going to need.
4. It sounds like you altered the program. May I ask why?
Incline decline are great for developing upper and lower chest.