1) Common BCI. Not bad looking, weight is good - he's nice and square [] like he should be. If he looked like this () he'd be fat.
2) Do not use a separate tub for feeding. Most snakes other than ball pythons remain "foody" for over a day after eating - where there is one rodent there might be another! Feed them in their enclosure. Moving any large, foody snake is begging for a nasty bite.
3) It's not clear from your post but I would switch him to f/t rats also, if that's not what he ate for you already. Eventually this guy could get large enough to eat jumbo rats, and a live jumbo can inflict damage on a snake very quickly.
4) I would set up a QT tub that's bigger than a 20L tank for him, to give him a chance to stretch out if he wants.