and there were just a few frames of bees. I think I saw some brood, but will wait a few days to see if any is capped by then. .
You must now limit the frame space as big as bees crew the frames.
If you have possibility to build insulated box for bees it helps a lot.
If you have 5 frames bees, you will get normal hive.
If you by a styrofoam insutaling board, from that you get easily proper box.
is there any need to feed the bees, since there is plenty of honey? .
No need for that. Keep your honey and give them later on summer. Nosema may be the killer of bees.
I am thinking that I should so that I can give them some terramyicin. Also, is the mold anything to worry about, or is it there because there was some moisture on the bottom board?
After winter there is many kind of mesh in the hive. Moisture is normal on bottom board because, when warm air meets the cold surface, it makes droplets.
When wether is good, close hive's upper entrance. Bees learn to find lower entrance during day. First they try to go through upper entrance.
I have used terrarium heaters with that kind of case. I have got normal hives from those "few frames hives" and they have brought 180 lbs honey next summer.
Most important, give them warm insutated box and take away extra space.
Later see if brood is porous. Give terramysin, if you see collapsed larvas. Also chalk brood can attach that kind of hive, but for that warm hive is the best medicin.
Put lower entrance small, not bigger than one inch. If they ventilate much ouside, make it bidder.