If you already put the medicine in, you need to remove the frog from it NOW. They don't react the way a fish would, it really could kill him. The maracyn could work, but heavy medications are a last resort as they are hard on the betta. Start by doing daily 100% water changes with 1 tsp of aquarium or kosher salt per gallon, make sure the temp of the new water is the same as the old, so you don't shock your betta. Make sure the temp is at a steady 78 degrees. You need to buy a heater, unfortunately there is no way around that, unless you want to heat your house to 83 degrees.
No the frog definitely needs more room than that. Here is a little excerpt on frog care from fishlore.com:
"Your Frog's Home:
They do best in a stable water temperature of 75-80F
You should allow 2.5-3g's of water per frog. I have 2 in a 5g mini bow with the filter setting on low.
Too strong of an intake can suck up their little flippers. Too strong a current may prevent then from getting to the top for air.
Ideally it should be between 12-18" high. Any taller your frog might have trouble getting to the top for air before tiring out.
A lid is a must. They're great escape artists and can squeeze through a tiny space.
Avoid gravel that can fit in their mouth or has sharp edges.
Small smooth river rock works well.
Plastic, silk or live plants will make your tank look nice and give your ADF a place to hide.
A cave is a nice addition, again, make sure it doesn't have sharp edges.
Only use aquarium safe products and make sure any holes are large enough for the frog to swim through.
A stuck frog will drown."
You can read the rest of the article here : http://www.fishlore.com/fishforum/am...arf-frogs.html