Hi. I see you are new. I'll help all I can.
To start, welcome to the world of aquarium keeping! It is a great hobby. And fish are some of the best pets I have ever owned. I think you'll love it!
Bettas can thrive in 1.5 gallon tanks with a few Ghost Shrimp and a snail. One or the other, but not both. And certainly not with any other fish. So you could keep him in there.
a 6.6 Gallon is way too small for Ghost Shrimp, and Apple Snail, and Cory Catfish. From personal experience corys CAN infact thrive with only one friend, but it isn't reccomended, and still your tank is too small. There isn't a dwarf cory Catfish. Only pygmys. You could have those, but not 'dwarfs'. Those get 4 inches (trusts me I have one) and need 10 gallons.
Do NOT get a female betta. They can not live peacefully. He will kill her. You only put a female with a male for breeding and under close supervision for a short time.
You can NOT have just 2 female Bettas. One will kill the other or both will die. You need at least 4 (5 is better and even more is awesome) and a minimum of 10 gallons for the 4.
I would just get rid of the corys and keep the Betta, the shrimp, and the snails in the 6.6 gallon. That is an AWESOME home. Way better than 1.5 gallons! The bigger, the better.
*2 Bettas (for now RIP Ryu) *2 Goldfish *9 Guppies *1 Gourami *2 Chinchillas *2 Budgies *2 Dwarf Frogs *1 Dog *1 Cat *2 Hermit Crabs *2 3gs *1 10g *1 Pond *2 2gs