Well....
I had to cut my son off the breast, cold turkey, at 15 months because I had to have a hysterectomy PRONTO.
He was obviously eating solid foods, etc, but had never had a bottle. He'd never had formula. My poor husband was left for a week while I was in the hospital to care for a baby that was used to the boobie and loved it.
We had a gigantic house. My son actually had two cribs. One in his own room and one upstairs in our room. While Mommy was away, my husband just had the kids upstairs with him at night which was on the total opposite end of the house from the downstairs kitchen.
He made bottles for the baby at night, but was so worried about anything spoiling. So...male ingenuity.....he put ice cubes in the bottles estimating melting time and liquid ratio.
Guess what. When I got home from the hospital, my son was totally weaned from the breast BUT, he would NOT take a bottle unless he could shake it and hear the ice rattle in it. It turned out he liked his bottles cold and I guess the shaking it like a rattle comforted him in some way.
Then, we had to break him of that eventually. And, he wouldn't take a sippy cup unless it rattled either.
I'm not sure you really need a mini fridge. My bedroom took up the entire top floor of our home and we certainly had room for one, but it wasn't a necessity at all.
I'm pretty sure that formula will be fine at room temperature overnight.
Just my opinion and best wishes to you.
I'm sure you'll work something out.