There is nothing wrong with using a retainer during the day in Ramadan and dry deposits do not affect that.

If you follow the view that hijama breaks the fast, then you have no right to treat a fasting woman with hijamah, even if she follows the view that hijamah does not break the fast.

If you swallow a bit of skin from your lips by mistake, or you could not find it, or it is too difficult for you to take it out of your mouth, so you swallow it with your saliva, your fast is valid.