I've only had my snake for about 2 months now, but I've been feeding him in a separate "enclosure"(it's just one of those white USPS boxes) and I've never once had any trouble with him eating f/t mice. I keep doing it not because I'm worried about him being aggressive if I feed him in the tank, but rather because he's now come to associate being put in the box with eating. I usually put him in while the mouse is still thawing and he spends the entire time searching for the mouse. When I go to put it in, he strikes instantly with no issues.

As for moving him back, I usually wait until he's done swallowing and has started to move around a bit more before taking him out. So far, no mice have come back up.