Tenant-1 only wants to finish out the lease (not start a new lease), he doesn't think he can find a subleaser for the last few months, and on top of that he "didn't sign up to live with a random roommate".I'm trying to be sympathetic with the COVID situation but I'm not sure what to do. 

If you are house-hacking with multiple roommates, I would limit occupancy to one person per bedroom.

That being said, now is not the best time to look for roommates to share common spaces with so that is something else to think about.

One, I'm confident will be completely rented out because I knew someone who wanted to move in and just needed to find roommates.

I have couple roommates that live with me.

I rented a house myself during my Senior year in college and had two roommates (both of which were my friends).I agree with @Annchen Knodt - renting by the room would be tough.  

Typically house-hacking is considered living in one of your units that is part of a multifamily or a roommate situation and letting others rent absorb your living expenses.  

Roommate situation and corona concerns have them staggering move out.We will refund any unused last months rent as a help and incentive and are helping with moving costs to facilitate this.

The bottom unit I was going to rent to for $850 while I live in the upper unit and have a roommate who pays $600 in a room for rent situation.

She would find a roommate once the pandemic is over.