I think the only thing you can do for the anus is to just stop inserting anything there. I think over time, if you continue to insert anything larger than your middle finger, it will probably continue to stretch, but if you give it a rest, at least stop for awhile, it might return to closer to your normal size. As for the T inj’s, I would not think injecting just a couple times would have much affect on your penis size.
How long have you been injecting Test? It’s pretty common that fur guys who’ve done it over several months or so, the penis & testes can shrink. I think what happens is your system detects very high levels of T & then shuts down your own natural production of it. This can also lead to issues w/ ED, sobthis is smthg I would discourage anyone from messing with. I’m not sure if your genitalia will return to normal after stopping T inj’s, not sure but I think some of these changes could be permanent (non-reversible) if you’ve been doing it for quite awhile...
As for the anal issue, if you've only experimented w/ this a few times, it’s possible it may return to near-normal if you stop doing it. I don’t think the premature ejaculation is related to anal stim, might be more related to your use of Test...