The biggest lesson learned: if you make changes to Bitcoin mining or pool software, USE TESTNET!!!!
you can also use Regtest for a purely private test network. and soon Signet (not sure how soon), that will allow 'members only' public testnets for more experimental testnets.
(1) I don't think this is anything but bitcoin-cli getnewaddress gave me an address that I used as the pools address (it began with a "2" and testnet=1 was set) but my blocks were found by the above address beginning with an "m". I assume they equate to each other.
I've forgotten the specifics of the 'm' addresses', but I don't think the equivalence thing is correct. Maybe NOMP won't accept the "2" addresses? "2" is the testnet counterpart of "1" legacy addresses (compressed or uncompressed IIRC), whereas the segwit native testnet addresses are... I think "bt1"(5) Looking at the blocks in the link above, I notice that the blocks are getting confirmations. I'm not sure how many are required before (fake) payment but I doubt that payment is coming.
should be 100 blocks to coinbase maturity, assuming it's the same as mainnet. Mainnet used to be 120 blocks coinbase maturity, cannot remember when it was changed, or if testnet (this is testnet3 you're using) was ever changed tbh.