Help me ID this spider!

Saw something in my peripheral vision crawling around my room. I originally thought it was an ant, so I was about to go in for the kill, but after looking closer, I realized it wasn't an ant and that it was a spider.

Anyone know what he is? If it helps with identification, I'm located in Florida. I'm also assuming he's a juvenile.

Sosticus sp, a gnaphosid

Neat! I plan on keeping this spider. I have only owned preying mantises, but would like to expand my collection. I was planning on a scorpion to be my first arachnid, but after catching this little feller, I think I might dive into spiders first.

How would I house this little guy? I have plenty of plastic cups w/ lids (ranging from 2oz - 8oz) from purchasing many mantises on the internet. Considering how big a mantis nymph is compared this little spiderling, I'm guessing one of these plastic cups should do fine for the little guy.

How about substrate? I have coconut fiber substrate that I use for my mantises. Would this work fine for spiders?

And for food...What do I feed this tiny juvenile? I'm assuming fruit flies? Is there anything else I could feed him? I don't want him to be stuck to a single item for his diet, I'd like him to have a variety of prey, but there's not I can think of for a spider of this size. He's about the same size as a freshly hatched cricket.

I also found a gnaphosid sling, very tiny! It has been eating prekilled roach nymphs, I put him in a deli cup with a thin layer of moist coconut fiber. Hope this helps!

It's likely that's either a sub-adult or mature. Most gnaphosidae are small in general.. the largest in the USA is Drassodes neglectus