Calcium deficiency and kitten teeth?

I have two questions.

1. So my kittens may have calcium deficiency, the vet didn't think so but he judged based on the calcium that's supposed to be in the commercial food. I think the way they walk is weird. Their back legs are not as straight as you'd expect them to be. How can I give them more calcium? Is it ok to give them calcium pills? Will dog or human calcium pills work? I don't see why not because calcium is calcium, but still. What if they get too much of it? Could there be any side effect? Is it OK to give them lactose-free milk?

2. Their adult teeth are growing now. One of the kittens has already lost most of his baby teeth, at one point he had 4x of the long ones on the upper jaw but 2 fell off. The other still has 4 for example. This is natural but is there anything I need to keep an eye on? I'm no longer giving them anything that needs chewing for treat etc. They never ate dry food anyway so they are eating solely canned soft food atm, I don't want them hurting their gums. Or is this wrong?

Thanks.

Too much calcium can result in constipation.

Human calcium pills may contain other ingredients besides pure calcium and the amount of calcium is likely too much for a cat.

If you think the kittens are walking strangely, you can seek out the opinion of another vet.

I wouldn't worry about the baby teeth falling out. Kittens are fine until their adult adult teeth grow in. They never seem to be in any discomfort. There are kitten teething chew toys you can buy if you want the kittens to have something to ease any pain.