Yes, I agree, coming up with one's own ideas to counter Watson, for starters ditch the lines proposed by Tzermiadianos.  No offense, moving on with the times and with developments sometimes means doing changes such as these.

3.Nc3 still would be my main vs French, for all levels.

"As always happens, there is no line that will last many years in the theory, and French expert John Watson has come up with a lot of interesting ideas against my proposed variation" -- Tzermiadianos in YB 105

I've had great success (+4=1-1, 2194 performance compared to my usual 2003) with a repertoire based on Tzermiadianos' How to Beat the French Defense. It's based on the Tarrasch and there are lots of almost-main-lines (i.e., he deviates but on move 9 rather than 4). Honestly 1...e6 is the move I like most to see.

I need some serious help sorting out my struggles from the White side of the French.

Some background for understanding: I am ~2100 FIDE, getting back into competitive play after a few years hiatus. I am looking at future long-term competitiveness, and so am looking for an opening I can feasibly stick with for the foreseeable future. Main goal is to be competitive at 2200-2400 level. I have no qualms with deep study and learning theory if necessary (and am doing so in several other areas of my repertoire).

I was a 1.e4 player for my first 6 years of play, from beginner up to 1800. In 2005 I switched to a Catalan based repertoire. I scored well with that, but never felt entirely at home. I've decided to move back to 1.e4. The French is my primary struggle to come to grips with, as the literature is pretty saturated on the Black side of things currently.

I've always performed best with side variations of Main Lines, where I can throw the game into slightly original territory, develop some ideas of my own and battle it out from a solid foundation. Slight advantage positions where I can neutralize counterplay and let my opponent stew and self-destruct have always been huge point-scorers for me. In my early career I was a Tarrasch devotee. These days I can't find a line that I feel confident in, I feel like Black is in a pretty happy place in terms of theory there. I've toyed with 3.Nc3 as well as the Advance in some online exploration, but have yet to find any positions in them which feel comfortable. They don't seem to click for me intuitively, and I again feel like Black is satisfied with theory as covered in recent literature and advocacy for Black's cause.

So in frustration I turn to you. No other openings feels as threatening to my 1.e4 prospects as the French does right now.

Well, a little unfair perhaps.
Just the KG book that was delayed.
Otherwise they have been rather prompt I think.
(and no, I have zero connection with QC, just a customer)

I understand that "Playing 1.e4 - Sicilian & French" by Quality Chess is going to recommend the Tarrasch. Not sure when it'll be written though - the other (supposedly earlier) volume on 1.e4 doesn't have a firm publication date either.