1997 Chevy Blazer Engine no longer starts

On my 97 Blazer, my problem started a little while back when it would not start (what seemed after a rain storm) sometimes. After a a few hours or so it would start fine and run fine for the most part. It did seemed to have some very minor stumbles while running.

Recently the problem has gotten worse and simply wont start at all anymore.

My diagnosis; we checked for spark at the plugs. Fine. We checked for fuel with a gauge. Fine. We sprayed a little starter spray in the intake which would cause the vehicle to start for a few moments. So pretty sure its a fuel problem; injector problem or ecu. If its a injector problem could they all be acting incorrectly in uniform to each other? And if its pump related wouldnt it run at an idle alot easier than running at 70 mph down the interstate?

Neither of these are inexpensive to replace, how would I tell which to start with?