Some Things Never Change

After I got done with the work I did out at Bob Rivers' place with the caulking and sealing I was pretty sure I was God's gift to the traditional boat world.
Not so much.
It's true that the seams I did fix are completely watertight. Kosher. Chapter-and-verse street-legal.
As far as I went.

That's actually Bob Rivers in the background there striding purposefully with sander in hand. Helped a lot, and I gained a new appreciation for the kind of man that does things and helps you and is manly and plain spoken and honest.

But there is a lot more to the apple than the skin.
I need to get back in there and really do all the rest of the seams and it is turning out to be an enormous task way over my head.
The little tombstone transom, a lovely piece of wood, represents a different challenge and I don't know if I am up to it.
The seams on the bottom are one thing, between boards that are tightly fastened to the frames and futtock blocks, so the challenge there is to bridge between planks that are fixed in place and the variable is the swelling of the wood that moves the edges slightly closer together when they are wet, which is allowed for in the caulking process. Everything is slightly flexible.

This rubber crap was in all the seams I got it out of there finally on most but not all the seams, inside and out

Around the transom, a simple slab of thick wood, there is a different issue. The ends of the side planks fasten to the edge of the transom, and that joint shouldn't vary or change dimension, but it did.
Are the fastenings loose? Unstable? Or did the transom plank shrink so much that it pulled away from the planks and cracked the seal between  them? If I put some caulking in  that joint and some Brown30 seaming compound will I just pull the fastenings looser?
Is it too late? I've been running around on the river, and hauling up on the beach, and now there is a fine layer of river sand all over the inside of the boat. There is also sand suspended in river water. So the crack that leaks now has sand in it. Even if I were to draw the joint up tight with fresh fastenings it might still be compromised by the grains of sand in the crack.

The cracks go all the way through, and inside the boat they act like sand collectors so the plan was to run a bead of wet-patch roofing tar in there like the old timers talk about

I'm tempted to go the whole hog, bring her into a real boat shop and take the fastenings out and re-fasten plank-ends to the transom. Lay a strand of candle-wick into the joint and bed the ends with Brown30 or with blackjack roofing cement like Captain R.D. Pete Culler recommends in his book "Skiffs and Schooners."
What I think I will do first is to haul her out and turn over, and take a Stanley knife and cut the crack open just the tiniest bit, and then run some black jack or some  brown 30 into the joint and then paint that over and see if it does any good, on the assumption that the fastenings are ok and the seam just got started with drying out up in Ballard in that garage/tent thing where I found it.
Then there is the entire seam I missed on the bottom I didnt even see it but it is a full length seam that still has that latex crap in it. That's gotta go.
I always do what I can see as best I can but there is so much that I simply don't see, that never occurs to me until something rubs my nose into it repeatedly. That shit never changes