TRT doesnt really make you any better or worse, just makes you operate the way you should operate or operate the way before you had low t problems, that is if your on testosterone replacement therapy (TRT) for low T and not just taking it.
As far as beating it a day before is to far ahead, if you are wanting to do it then I would do it a few hours before you go. Beating does help people that have premature ejacualtion. To be honest with you its a hard thing to control and the younger you are the harder it is to control. Second off a lot of its mental the more you think about and the more worked up about it you are the more problems you are going to have. If you are worried about make sure you please her and get her off first by eating out and during sex stop and fool around some more. As long as you dont last 30 secs and she gets hers I dont think most women are going to be that caring if you last 3-5mins vs 30mins. The median time for length of sex is around 7mins not including foreplay. As far as cum amount if this is a new girl i suppose your using a condom so shell never see it, and if you are not most women are concerned being pumped full of a gallon of the stuff.