I wouldn't use bleach, it'll stick around to much even after a good cleaning, but yes bleach kills 99.99999999999999999999999999999999999999999% of all microorganisms, good and bad.
Just use white vinegar and water mix, clean a few times, scrubbing the whole tank well. As for substrate, I'd say just start over with new stuff to avoid any issues or worry.
Rams, one pair for a 29 gallon would be enough. You can get a few and let them pair off, and take the extras back to the LFS. But most likely once they paired they'll harass the others into death. So you can either get a 'pair' from a breeder/aquabid, or make the deal with the LFS to return the extras.
I wouldn't suggest angels in there, its not much space, but more that its not much water to displace the poop/food they use. Rams a very good choice. You can still plant with them, they love plants. You can get easy plants in the crypt/sword line that will also transfer well when you upgrade. I've never seen mine use caves, but I've heard they like them, so keep that in mind.
As for QT time.... Play it safe, keep watching it for a while. I'm not expert on what you had, but I would always veer on the safe side.