So I've been working a lot on my tub and getting my doors back aligned.
I looked at your pics on the 1st post, assuming they still look the same, here is what I would do.
First, remove your striker post. Tighten all the body to frame bolts. At this point, I'm assuming your gaps still look like the pics in the 1st post. I'd also pull the door off completely, but that is just me.
Second, attempt to get the B-C measurement as close to 39". You can do this by shimming up the front core support body mount. Or possibly using a come-a-long, ratchet strap, or other made-up tool pull the A pillar (measurement B) towards the rear of the truck (loosen the front core support mount while doing this).
Third, when you get the measurement close then you can start messing with aligning the door to the quarter. Don't worry about the fender gap, address that after you get the door aligned to the quarter. You can shim the outside 2 hinge bolts to move the door back towards the quarter, or shim the inside hinge bolt to move the door forward away from the quarter. You can shim the uppers or lowers differently. Get the rear door edge square to the quarter with a nice gap. Then, if the door sits low in the door opening, you can jack and shim the front tub body mount (under the drivers feet). If a roll cage (with front cage)is installed, you'll have to unbolt it before trying to lift the body mounts & shim them. You can always slot/ovalize the holes in the hinges to give you more room to raise the door. With the bend in the body braces, all bets are off, and you'll have to break a few "rules" to get the door right.
You also want the door closing evenly to the window frame and even to the quarter. Move the lower hinge out to push the top of the door in, and vice versa. Once the door closes nice in the door opening with no interference or pressure, then put the striker back in and adjust it so it holds the door tight to the weather stripping. The striker should not pull the door up or down as it latches. Put the striker in to match the nicely closing door.
Then worry about getting the fender to front door edge looking good. The fender is very easily moved & adjusted, compared to the quarter panel.
It's really a step by step process, looking at the truck after each adjustment before making the next. I'm super close to getting my gaps right (my truck's body is a mess from PO roll over & lots of abuse), I just need to pull my cage so I can jack up my front tub mounts and raise the doors a bit.