Gary Mitchell

honestly the General exam isnt that bad, i was dreading the electrical theory sections too but most of the questions on the actual pool are pretty repetitive once you drill them with HamStudy or something like that. i think i did maybe 3 weeks of studying, maybe 20 minutes a day on the app during lunch and i passed without too much trouble. the formulas are a little annoying but you dont have to understand them deeply to get the right answer on the test, just recognize the pattern.
as for HF being worth it, i was exactly like you for two years just doing VHF and then i finally got on 40m and it completely changed the hobby for me. there is something really different about throwing a signal across the country or catching a station in europe on 20m during a good opening. you dont need a fancy station either, even a used Icom 7300 or a Yaesu FT-891 and a simple wire antenna and youre on the air. 40m is good for regional stuff especially at night, 20m is where you get the DX during the day. just get the ticket first and figure out the gear later

just took mine last month, was a tech for almost two years. i used the Gordon West book and also did the HamStudy flashcards. took me maybe 3 weeks of casual studying. the propogation questions got me a little confused at first but once you understand basically why HF works the way it does it clicks. passed with an 87 i think.

i built something similar last winter and had basically the same problem. for me it turned out to be the transformer balance more than the diodes -- i wound my own trifilar on a binocular core and i guess one of the windings was slightly off in terms of turns ratio which prevented a real deep null no matter what i did with the pot. rewound it being really careful about keeping the wire twist consistent and it got a lot better, ended up around 45dB suppression which i was happy with. might be worth checking that if you wound your own transformers.

congrats on the first build man, that cold solder joint thing is basically a rite of passage. i think ive reflowed half my projects at least once before they started working right.
the QCX mini is genuinely excellent for what it is. ive run mine on a 3s lipo with a small buck converter keeping it around 9v and the efficiency is pretty impressive, you can get a whole afternoon of POTA activations out of a reasonably small pack. the built in keyer and filtering is so much better than a pixie that its kind of not a fair comparison. for hiking its really hard to beat the size to capability ratio. only thing i'd say is the display can be a little hard to read in bright sunlight but thats minor.
if you want to go even lighter look into the uBITX v6 once you're comfortable building more complex stuff, but for now i think the QCX mini would make you really happy and its not hard to put together at all.