Are you sure of the sales price for your home? Do you want to get rid of it due to the problems or are you tired of being a landlord? How long have you owned it? This plays into your tax issue or if you are looking to continue as a landlord you could do a 1031 exchange and buy another rental property.
There are ways to list your property for far less than the commission mentioned by the previous agent. If you are interested in talking in more detail feel free to drop me an email and we can set up a time to chat more about your options.
Say you sold the home at 79K, paid a 6% agency commission = $74,260 - 20% (estimate) capital gains tax = $59,408 - title fees = roughly $58,000. - potential closing cost assistance to the buyer and home inspection repairs. Doesn't seem to leave you a ton of money to pay back your dad... & the roof repairs and water heater are going to be noticed by the home inspector...
If you rent the home, you seem to be making a + of $300 per month which covers your payment to your father, however you would need to sink at least $800-$1200 for the water heater and depending on the size of the home a few grand for the roof. Not sure what the plumbing repair would cost you.
Sounds like you need to figure out if you can swing the repairs before trying to break it down any further. Also, if you didn't sell...how long would you hold on to the house? If it was only for a few more years doesnt sound like you would make up the cost of completing the repairs. But if you are in it for the long haul it might make sense to hold on to the unit.
I would sit down and consult with an agent that works your local market and see what their market value estimate is as well as get some estimates from contractors about the work... Gather your figures.