Starting Point for Room Treatments?

I’ve focused on tweaking my system for too long while ignoring proper room treatments… In the meantime I’ve been placing outdoor couch pillows against first reflection points, and draping a quilt over my large TV. While embarrassing (especially when demoing my system to friends just getting into HiFi!) all of this makes a massive improvement, especially covering the TV - although I do find that while vocals and sounds in the center of the image become concise and in-confused with the blanket over the TV, it definitely over-dampens things. I have an odd room - open concept upper floor with my system at one end (but with 7.5ft clearance from the one corner that is near my right speaker. 12ft vaulted ceilings (a-shaped) with the apex pretty much above my head in the listening position, with the ceiling slanting down towards my system to a minimum of 9 ft. There is an island that forms a 4ft partial wall, to the left of my listening position. One of the first reflection points is on this wall. I have engineered hardwood over a suspended floor (ugh…). Thinking I MAY need 1) Treatment on the island/partial wall on my left, and 2) Treatment on the wall to my right that extends up to the 12 ft ceiling peak (but treatment only up to 5ft high), 3) treatments behind each speaker, 4) treatment on the ceiling in front of me (when I look at this ceiling my line of sight is perpendicular to it). Maybe a small rug too. Finally the tricky one: suitable treatment I can hang over my TV when we are not using it - maybe by adding hooks or clips. I don’t really know where to start, figuring out if I actually need all of the above, and figuring out the right type of treatment for each spot. And, do I need treatment only or sound dispersers as well? Do I go to a website and punch in my unconventional room dimensions and trust that it gets it right? Do I get a consultant? Do I buy stuff and start experimenting - and if so what do I buy? Not sure where to start! Looking for some pointers. One more thing - there are large windows 7ft behind the listening position but there are soft fabric blinds covering them that I close when listening. The couch is about 8ft away from each speaker - fairly close which I found improved the sound in my larger space…. I have no major problems with the sound but my makeshift treatment obviously is sub-optimal. Also, the sweet spot for my B&W 802 speakers is like a laser pointer which is really annoying. Image starts going wonky just a couple of inches off dead center…. Thinking this is an attribute of the speakers but could be the room? Yes, I’ve relentlessly experimented with toe in and ended up with my speakers only very mildly toed in a few degrees. With the vaulted ceilings I have a lot of flat surfaces that have a perpendicular line of sight to the listening position…. That said I’ve had really bad rooms before and this one isn’t bad at all, provided my setup is semi-“near-field”. No bass issues, etc. Any advice is welcome…. I am not the type that will be happy just punching dimensions in a website and buying some expensive foam…. I know for sure if I do that I will end up experimenting relentlessly and eventually realizing how much better I can get things with a different approach.