I recently got a 10 y/o chinese elm and it appeared to be entering dormancy, but in coming back to Philly, I'm getting a ton of sprouts (which I thought was good), but probably isn't because chinese elm are supposed to be dormant in winter. I may have overwatered it. It's beginning to snow and I don't want the cold to harm my tree, but I heard dormancy makes the tree "happier".

Did I completely mess up my tree's cycle? Is there a safe way to get it back to dormancy?

indoor and dormancy is two words that does not have any sense together

If you’re worried, put it outside if you can. Elms are fairly hardy and can endure cold and a little frost. Putting it indoors (and they are often marketed as such) effectively creates an evergreen as it won’t drop its leaves in autumn/fall as it usually would.

Not allowing a tree to enter dormancy won’t kill it instantly, but over 3,4 maybe 5 seasons, it will begin to struggle. In essence, the tree is continually depleting resources and exhausting itself.

Sometimes the things we do — or don’t do — to our bonsai don’t show up until later down the line, making it difficult to understand where we went wrong. It’s all learning. Lots of info on this site so do check it out.

Thank you for the advice. So if one season of non-dormancy won't cause very much damage to the life of my bonsai, should I even bother to get it back into dormancy? There are a lot of new sprouts that are now 2-7 inches long so my worry is that bringing it back to dormancy would do more harm than good seeing that it's already pretty far along in the early growing stage and would just interrupt the growing cycle that my bonsai thinks it's on.

I see no realistic way to bring it back into dormancy. Just care for it the best you can and in spring, after the last freezes, bring it outside.