Does anyone know how to calculate the rate of repair for SCVs? (As in how long does the build time have to be for a unit to have a heal rate of 2 per sec.)
Also, does anyone know the rate a medic heals per second?

I don't know about the scv, but a medic heals 2hp per second.

Medic heals 2 HP per energy. But energy goes down much quicker than 1 per second.
A medic can heal about 23 HP in the delay between a guardian's shots. I'd say that's about 1.5 game seconds / 1s real time.

About the repair, if I'm not mistaken it's equivalent to the build time. At the very least its directly proportional to it.
15 units of build time in ScmDraft (1 for Staredit) is 1 game second.

For both of it you could easily make a testmap and make sure the values are correct. It's a matter of 5 minutes and surely faster than waiting for a reply.