[jdl22]

It's pretty simple, a raise must be at least the amount of the previous raise. You raised it 350 (from 0 to 350) so he must raise it to at least 700 to make it a valid raise. Since he didn't it doesn't count. Yes you must take his stack size into account when making raises.

I know it's frustrating when you don't plan it out in advance. Think of it this way. It's something that makes the game more complicated. Since you are the thinking type of player it is to your advantage because your opponents won't do the planning you described.