I've been running this for a few days and have found a few small time saves:

Quickest Predator Kill:- The grenade will always trigger the checkpoint and bring him down to melee combat.

Tequila Manipulation. This only works after you've rescued her from the Ruins and have cleared the next area of Xenomorphs. When she says "I'll get the door...", melee and she'll chase you. Repeat until she's at the door.

I have no idea how to do the Refinery roof skip after several hundred attempts, so Corpseflesh should be able to bring his time down even further with these small strats. I should be able to get a 53:XX without that skip, and better general combat.