Keep it and make the offer to your downstairs tenants to help find the new tenant-that way they have a sense of ownership about the new person, and will serve as de facto landlords while you're away. Plus if they know each other they will be happier, which is all that matters.
Also, being 80 minutes away isn't going to keep you from popping by, maintaining that relationship, and being able to address emergencies as they arise.
I'm guessing the rents is the projection for when you move out? Making over $500 a month plus principal payments plus the hidden depreciation costs for tax purposes makes this a great return.
If you want to sell it, after closing costs, you won't make that much money. Also, it is too bad you're only 18 months in. At 2 years of living there as a primary residence you can sell the property with no taxes on any profits made from the sale--but it sounds like that will be minimal.