You are going to get married, do get married.
Sperm is not like a bucket that you have a fixed amount for whole life. The more you spend the less it will get. Its a bodily process and a continuous process. Sperm keeps producing, as scientist have discovered a male embryo keep having immatured sperm when he still isnot born.
If you have too much of a concern, you can go for a test on your sperm count. That will clarify if you can become a father or not.
Sperms do not dry up just like the ink dries up in a pen when you use it repeatedly. The sperm levels hold up depending upon your testosterone levels, so what you fear is absolutely ridiculous. For getting clarity on this, have a sperm count test prior to getting married, that would give you a clear idea if you can become a dad or not.
However you will need to limit the frequency of your masturbation, because regular masturbation would result in loss of erection and addiction to hand-jobs rather than the actual sex in the future. So try to limit it to a mere 2-3 times a week. Rest of the things are pretty good. And remember to engage in safe sex while you have it, because unprotected sex has the risk of transmitting STD’s/STI/s or even unwanted pregnancies.