Well 750 is pretty impressive, Im glad you did have it checked after you changed doses, so that clears up any concerns I had. As far as doses go, of course you know it varys from person to person, but anything over 1200 is high(anabolic range) in my opinion.
And you can do the math yourself, I think its something like this, 7.5g of gel equals out to 7.5mg X 7 days = 52.5mg of actual test per week(this may not be 100% accurate, see the trt forum for the exact numbers) and with injectable test there is a percentage thats actually not absorbed/usable/available(not the right term) so 100mg inj test is actually something like 70mg, so with that info, if you look at some of the cycles posted about here where guys are doing 500mg of test a week, they are actually getting like 400mg+/- of actual test, but the problem is what is there blood level and how much is wasted/overkill.
Essentially, with all this, what Im getting at is, if you can get 1300 from 10g and you add something else, or more gel, you have got to be hitting the anabolic range, but you still have to worry about e2, estrogen, dht conversion and whats wasted also. Again, I dont have the numbers on these, but see the trt forum and you might find the answer there, but they tend to shun posts about using anabolic amounts for gains, rather than for prescribed trt. But you may still find some answer there if you "word" your questions correctly.