I doubt very much that you are getting any extra benefit from taking 2.5mg. Look up the curve that shows DHT suppression at different dosages. It's negligible even between 0.5 and 1. Your wallet will be better off if you lower your dose but don't do it because of this post. Do more research and come to a decision.
Also just to point out, Finasteride itself causes an increase in Testosterone. Remember, it's not being converted into DHT as much as before, hence more circulating levels of it. You may actually experience better gains in the gym. My personal blood tests have shown that my testosterone levels have been consistently higher than before I was on Finasteride. Thankfully it's not being converted into Estrogen as those levels are roughly the same and within range.
Ps. I'm in the gym training 4 times a week. No issues here my friend. In fact i'd say i'm actually in the best shape I've ever been in. Don't stress.