These must have a ridiculously fast metabolism to be able to raise a 100 or so joeys at a time. I presume that, based on the comment that it must constantly eat, that it consumes its own weight in food several times a day?

Yes, it does need to eat constantly. I assume its birthrate is possible because stem mammals had a similar birthrate before they traded it for a bigger brain.

Stem mammals had hundreds of young? I'd accept it having twenty young, but...I still want to see the data. Alpha has lower scientific plausibility standards than Beta, but I've simply never heard of that before.

The fur detail looks nice.

There's evidence of some with 80-some babies. This doesn't get into hundreds plural that find a nipple, just 100-some. I figure it's a probable increase from what stem mammals did with the fact that these ideally have more refined milk-making ability than those stem mammals--the stem mammals probably sweat milk, which I think is a lot less effective than having a ton of nipples.