Some BPs seem to have color preferences, possibly the result of getting bit when fed live & thereafter fearing similar rodents.

Has he EVER eaten for you? If he was on mice & you're offering rats, that could be the problem...

Never a fan of "braining"...try NOT doing that, IMO it doesn't help. But if you want to release more scent from f/t, just pinch-damage slightly the nose using tongs.

Yes, yes, yes...that COULD be the issue, trying to feed when he's cruising the cage. Watch & wait, feed at night...don't over-do the 'zombie-rat-dance'...keep it very
subtle. Too much motion scares off some snakes. Approaching the snake also puts most of them off...it's not normal. Hopefully he'll either grab it tomorrow, or at
least seem interested. YES, I'd leave it just outside his hide if not grabbed...some are so shy they'll only take with lights out at night, so leave it & go, don't check
until morning. Cross your fingers! Sometimes we just have to figure out what our own snakes need...good luck!