Good questions. In general, 55F should be OK. There are several ale yeasts I prefer at that temp.
The flip side being that there are quite a few ale yeasts that will never ferment at that temperature.
Yep, but I must have avoided those because I've had more luck than not at that temp. Wonder what yeast is in a Mr. Beer kit?
I imagine Cooper's Ale considering Cooper's owns Mr Beer.
I would assume it's a clean ale yeast like 1056/001. The packets are usually just stamped "ALE YEAST". I started with a Mr Beer myself.. first tip I got was ditch the yeast. I'm sure it's perfectly fine yeast, but just the not knowing. Plus I like to make beers where the yeast character is the whole point, Belgians, German Hef, etc.
To the OP, I wouldn't ferment in a minifridge. In my opinion that's too cold. I ferment my beer at "room temperature" which varies from 65-85 depending on the season and I
usually don't have a problem. It doesn't need to be exactly the same temp the whole time, and you'd rather be a little warm than cold.
It's your first batch it may or may not turn out that great, but it's about learning the process. Don't get frustrated with it if it's a little squirrely. I don't have any kind of temp control and I do OK.