If you're set on 2X, stick to Shimano. SRAM isn't great at it. I have no problems with 1X (and therefore SRAM,) but I use an xD driver so I can have a 10T small cog-- 44/10 is kinda nestled between a 50/11 and a 50/12.
I see absolutely no problem with mixing and matching-- the levers and derailleurs are the only things that must go together.
I can't imagine going to a 180mm crank, and I'm roughly your size. 175mm cranks are plentiful and can be found cheap. Number of 2X 180mm cranks currently on eBay: 13. Number of 2X 175mm cranks currently on eBay: 1,151
The FSA Adventure is a great starting point for a flared bar-- they're really cheap and are pretty comfortable. Just buy one size up from what you'd usually buy, as FSA measures the width... weird. A 44mm bar is right on 42mm on the hoods.
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