My 5 cents as someone who's building several velobuild bikes atm, have ordered 6 carbon wheelsets over the years, have been using aliexpress carbon handlebars for years, weighs c.80kg, have never ridden gravel, sucks at MTB, and essentially only does road cycling:
Velobuild GF003 (it's very finished and looks super sturdy)
Sensah or Ltwo 1x (for your weight & steep stuff i think a 1x with the biggest cassette you can fit is best. It's very easy to run out of gears on a 2x setup)
I have had good experience with Farsports wheels, if you contact them directly by email you can configure a lower priced option than what they advertise (get Sapim spokes, the rest, afaik, doesnt matter too much. Get wide gravel rims). Buy from whomever though.
Spend money on good tyres, that correspond to the type of riding you will do most.
Steep + heavy = hydraulic, most probably? My builds are mechanical with Jagwire KEB-SL housing, but i havent riddem them yet so i can't speak of breaking performance. Although if you use mechanical + Jagwire KEB-SL brake housing + don't route everything internally (maybe route the front brake externally around the handlebars then into the frame to limit awkward angles) + 160 rotors (or more?), you're probably going to get a bike that brakes very well.
Budget wise, you should be below 2k. Not sure if you can get to 1.5k. Maybe 1.5k + shipping?
Now i may sing a different tune after i've ridden these VB frames, but so far, handling them, they look solid. You're heavy but i think we'd hear more horror stories if carbon frames kept breaking like matches. I have friends who ride mountain bikes like pro riders, i would not recommend them anything unbranded because i know they push equipment to the limits & racers should race race cars. Meanwhile, you're "just" heavy. If you hit a big ass pothole, you're more at risk of breaking your gear, but idk if this risk is materially higher using a velobuild frame and good wheels. If you pick aluminium wheels, the bike wont feel as nice, but they will be somewhat bulletproof and much cheaper. Something you could upgrade later on maybe depending on feel?
Happy riding!