Advice needed for DIY subfloor replacement and blocking installation.

"Decided to install LVP in the bathroom, and this is what I’ve gotten myself into. It seems like the previous owner didn’t care much about the house, as I’m constantly fixing or replacing something. Oh well—the joys of being a homeowner, I guess.

I was on a tight budget to hire a professional, so I decided to tackle it myself + learning experience. I started by removing the cement sheet, cutting out the rotted OSB, and now I’m trying to figure out how to add some blocking before placing a new sheet of OSB/plywood on top.

Here’s where I’m stuck: there are about 4 inches of old OSB left that I was planning to cut out, but I only have access to 2 inches because the rest is under the drywall. Should I cut the drywall to access the remaining OSB, or leave it as is and install the blocking?

Speaking of blocking, based on these photos, how should I place it? Additionally, the wall on the left side (by the toilet) is not sitting on the joist, and on the other side of that wall is a two-sink vanity.

Any advice would be greatly appreciated! If there’s a way I can buy you a coffee, let me know—I can Zelle or PayPal.

Thank you!"