Well hello!
Aw, yay, 13yro corn snake! I so feel you on being attached and owning one longer than any of your horses–that’s my Cleo (age 14 1/2) and Seymour (13 1/2)
Minus the whole attempting to swallow his tail thing, your boy’s behavior isn’t unusual necessarily in and of itself–but it’s unusual because it’s new for him. I have seen many overenthusiastic feeders bite at all the wrong things (like ME…c’mon, guys, haven’t you heard about not biting the hand that feeds you?), bite at the air, twitch, and lunge, and otherwise spaz out at OH BOY FOOD time, but not bite themselves.
So, my initial thoughts:
- He could be particularly hungry and thus overenthusiastic, and thus nondiscriminatory.
- His senses could be dulling as he ages, which coupled with food enthusiasm results in less accurate aim.
- It could just be a particularly bizarre moment in his otherwise normal corn snake life.
- There could be some sort of neurological deficit going on resulting in abnormal behavior, but you’d see signs of it in other aspects of his life.
My money would be on one of the first three or a combination thereof.
I’d still feed him in the tub and still offer him f/t mice as you have been, but maybe offer it on tongs so he’s like, “Hey look! That wiggly thing smells like food!” Give him a mousey pinata to target.
How often are you feeding him? What size mouse?
Also, this thread is useless without pics! 
Incidentally, one of the best reputed corn snake breeders I know posted a pic of one of her valuable offspring doing almost exactly this earlier this spring on one of the FB groups…so it definitely happens to even the most experienced and knowledgeable among us. Sometimes, they just do bizarre stuff that makes no sense. Sometimes, they’re like horses. 
My corn snakes seem to have some sense about feeding, at least usually–don’t mess with my ghost corn girl Alina, and previously pictured Cleo can be verrrry excited and indiscriminate. Now, my hognoses…welllllll…they’ll bite annnnnything, including themselves. I had one girl recently lunge at the frozen/thawed mouse offered on tongs–because they bite annnnything-- and miss, causing the mouse to smack her water dish. She lunged and bit the water dish. Then she proceeded to chew on her water dish, trying to get a better position to swallow the thing for a solid minute at least before giving up and letting go. All that time I’m dangling the mouse inches away from her. Another time, I was offering a couple small fuzzy mice to a different girl. My hogs don’t adapt to eating outside their enclosures the way my corns do, so I feed them in their enclosures but place them on paper towels to reduce the risk of ingesting substrate. Well! When I went to check on her, I saw she’d tried to eat the paper towel but thankfully spit it out in a corner of her enclosure. Forget it! I’ll just risk her ingesting substrate, because it’s a helluva lot better than eating freakin’ paper towels.
By the way, this is my snakey-themed Facebook page–lots of pics and stories and such on our mini-snakey-herd here: https://www.facebook.com/CleosKingdom/
Hope everything’s okay with your boy. Looking forward to pics, if you have any. 