With all due respect, I don't think it matters what your DHT levels or T levels were at, previous to beginning finasteride treatment.
I know this guy, 27 yr old bodybuilder who uses healthy doses of Testosterone injected as well. He is huge, 6ft2 230lbs, etc. High T levels and everything. Within 4 weeks of using fin @ 1mg/day, he was unable to get a normal erection. To this day he must use PGE1 injected into his penis for adequate sex with his partner. Nothing else works.
Fin seems to be more of a russian roulette than a calculated risk by getting before/after bloodtests... in his case, it did absolutely no good.