So, just based on what you've posted, here's my thoughts.
The condo seems like it's performing very poorly. Net income after regular expenses is 10500, which is only a 3.5% cash-on-cash return even with zero maintenance costs. Normally, I'd say to do cash-out refi, but the numbers don't make sense to do that either. Generally, unless the monthly rent is about 1% or more of the total price, it's not a great deal. And you're at about half a percent. So, I'd definitely sell.
But, your mortgage has a really low rate, so paying that off is really an end-game move. Unless you're ready to retire now-ish, I'd leave it for the time being.
Instead, take that 300k and put that to work for you. If you want to buy more real estate, I'm sure the cashflow from that would be able to pay your mortgage and more. Or, you could just drop it into a fund.
Just my $0.02, hope that helps.