The enemies make great use of destructible environment, such as ladders, trapping me repeatedly having to risk falling prone. The enemy focuses on lower AC characters and actually go for the killing blow when on the ground. I pushed Bernard through the window, down the tower and the next turn one of the other constructs kill shadowheart just like that.

As a veteran rpg player you will walk all over combat, a lot. That's what higher difficulties are for.

The current difficulty is normal for bg players and quite challenging for many new players. I think if it wasn't buggy and in early access, the difficulty would be spot on.
Aside from balancing issues and strange alterations to the dnd formula like shoving, jumping, ground effects, resting etc etc

It doesn't feel like it is DnD difficulty though, it's clearly something else and it feels too early to make changes to the rule set to see how it balances. It would be better to find out first, whether or not the DnD ruleset has to be changed.
I don't quite understand the priorities here, doesn't this take lots of time to do? Currently there is no comparison just how BG3 100% DnD would feel and play like.
But I've got no clue about the development structures in place, maybe it was tried already and found not fun.

Items are nuts sometimes and sometimes just nice. MM necklace and the blessing staff....I mean....thank you but maybe 100 hours later in the game...
The ring with +3m running speed or the "healing grants resistance" gloves, now those are great lower level items.

In general, please make use of the largest foundation any fantasy realm has ever known, and build on that more