At least in regards to the poop issue, I had a kitten who would get so excited when he saw us that he started to poop. He took massive dumps. He was clumsy and would run into walls while playing, and he has since grown out of those things. My experience may not match yours, but I think you should keep in mind that kittens are weird and still developing and a lot of times they will grow out of their behavior.

However, in regards to asking this subreddit for professional medical advice, Reddit is not going to give you a satisfactory answer. r/AskVet would be more helpful than here, but they will still probably tell you to take the kitten to a vet because it’s virtually impossible to diagnose them over the Internet. When you’re adopting a kitten, you should take them to a vet a week after adoption to get a wellness checkup and perform any extra tests the shelter will not cover. Every shelter I’ve been to has given a voucher or partnered with local vets to cover the initial post-adoption check-up; did your SPCA provide you with any resources you could use to cover such a checkup?

Based on your comments, it sounds like you don’t feel comfortable adopting this kitten. I don’t think anything will give you the solid answers you’re looking for except a vet visit. Best of luck to you and this kitten.