but don't have enough to rent more than ~300TH.
If you can't afford to rent enough hashrate to test your pool, then that's a problem to begin with, to find a block in the next 12 hours you will need 2EH worth of power, the current rate on NH is about 15.8
BTC per EH per day, so for 2EH and 12 hours that is exactly 15.8btc or $135,880, no way on the planet you are going to get that much hashrate while testing the pool.
Another ugly fact, since you mentioned fees of 2% it means it's not a PPS pool, and it's highly unlikely that anyone will mine on a small PPLNS block unless you would give them more than what the network would pay them, which you don't seem to be able to afford, now if you were to go PPS, then you will need a ton of
BTC in reserve, which you don't have judging by what you wrote.
I am sorry if I sound mean, I am not, I am trying to tell you the facts the way they are. sorry.