That is a good score on tactics. I belive that you should continue doing tactics (maybe 25-30/day?) and increase engame study a little (5-10/day?).
Should I head to TACTICS or ENDGAME?

Do both. Conserve a little bit of time for some tactics and then spend the rest of the time on endgame.

I have a rating of 1500 OTB and I, also, have a tactics trainer rating of 2200+. I figured the ratings where just inflated. I think until I reach something like 2700+ I should probably continue to study as much tactics as I possibly can because it is still due to tactics that I lose my games.

What is OTB?
You have a FIDE rating and don't know what OTB is ? hhmmmmm
LOL

Well, Internet ratings tend to be wildly inaccurate, though I practice my tactics on www.chesstempo.com, where I think the ratings are slightly more realistic.

2250 is inflated, but still pretty good for tactics trainer. I suspect your OTB rating may be a little deflated at the moment
Hey. Today I was stunned to find I could reach 2240 on the tactics trainer and solve a 2300+ rated problem. But my OTB is only 1600-1700....so 2240 must be inflated, but does anyone know how that compares in general to the chess.com population? Should I concentrate my studying to tactics (right now I'm doing 40 problems / day) or should I shift more to endgame study (right now I'm doing about 1-2 lessons / day from Silman's Endgame Course)?
I'm rather pleased on such a high score for tactics, someone just come in and burst that ego for me. How good is 2240 really for tactics?