last weekend was horrible as I could feel myself standing up and couldn't fix it. Any suggestions?

tee up on the range the height you would on a par 3, then hit half shots with just your right arm(7I or 6I). Make sure you are using hips and shoulders to hit, not just your arm. This will expose how much you are more than likely flipping.

I have been working on this as well.

For me, the most cliche advice in golf has really helped. Focusing on "keeping my head down" and actually seeing the dirt fly has made some big improvement. Sounds stupid but the video doesn't lie. Still not perfect but much, much better.

aggiebrother's comment makes me wonder, though… am I losing spine angle because I'm releasing my hands early, or am I releasing my hands early because I'm losing my spine angle?

I try to feel my shoulders pulled back a bit through out the swing...it helps me

Put something against your butt and hit shots. Make sure it's short enough that you won't hit it on the takeaway or follow through (stand bag, chair). There is a training aid out now that it can't remember the name. It's a yellow foam ball on an adjustable stick/stand that can be positioned for many types of drills.

BENDER BALL!

BENDER STIK, I mean...

the big misconception with "keep your head down" is you forget to turn you body. IF you can hit a chip shot with just your right arm your "head will stay down" The easiest and best analogy I can provide is picture how your body rotates when throwing a ball... your head is still but the body and arms swing together. same in a golf swing just the axis has been tilted at hips. people tend to think of what NOT to do rather than what TO do.