I rescued a baby betta from a friend who bought the fish not knowing the care it needed, so I offered to take the baby. I have baby in a heated one gallon unfiltered tank with a plant. I had a small internal filter in the tank but it made the water wayyyy too hot. I'm doing partial water changes once a day and so far baby eats anything I throw his/her way (crushed omega pellets, crushed flakes, frozen baby brine shrimp, bloodworms) and is very active around the tank. I've had him/her two days and baby is already coming out when I come into the room

When baby gets bigger I will move him/her to a heated, filtered, cycled five gallon.
My question is how hot is too hot for a baby betta? My heater is keeping the tank at 85-86 degrees and while I've read babies like to be warm I'm worried it might be too warm.
Also, can anyone estimate how old this baby is? For names, I'm thinking Fujimoto if its a boy and Chihiro if its a girl.