The future of bitcoin mining is already known. ~900 BTC / day for another year, then 450 BTC / day for four years after that, then 225 BTC / day for the four years that follow.

The hashrate doesn't affect the issuance nor the price.

Public mining ops don't really hold a ton of bitcoin anymore, ... from around between March through June, 2022, many miners had to liquidate much of the BTC they were holding.

Miners don't validate transactions. Well, the act of solving a block does involve validating the transactions before they put them into a block candidate, but their node validates the transactions only for themselves. My node validates transactions for me. Your node validates transactions for you.

Miners cement the ordering of transactions. That's their one job.