Are you aware that Itch's terms of service don't limit the number of downloads?
Itch is also a DRM-free system.
What I'm saying is, if you want to limit access and the number of downloads of your product, Itch.io really isn't the right platform. Not only does it lack any such tools, but its TOS goes in the exact opposite direction.
Note, I'm not criticizing you. If you want to add DRM and limitations to your product, that's your decision, and I respect it. What I'm saying is that Itch isn't the best place for that sales approach.