It's less complicated than you think. If you can find the room, about 4'x4', you might look into the Langmuir Crossfire Pro. It doesn't seem that the cost would be an issue, but it's less than $3000 with all the options. The water table knocks down the fumes, so your extractor would probably be adequate unless your garage is air-tight. Wastewater disposal shouldn't be an issue either, unless your city has a strict pre-treatment program (and you don't want them to know what you're doing in there). The table holds about 15 gallons I think, and quite a few of the owners have posted modifications to conserve water and filter out the metal; the new table fluids are mostly glycol based (no hydrogen gas), and DIY fluid is usually Borax based, once it's filtered, you just need to adjust the pH before disposing in the municipal sewer system. (Wastewater rules are a part of my job.) I would suggest using one of the pink colored fluids though, since it looks like soap, and the others look like antifreeze or porta potty water if they were to escape down your driveway. The Crossfire Pro has been in the wild for about a year now, and there are plenty of YouTube videos of the Pro and the Original in use in small garages and workshops - now that I think about it, I might be the only person that's got an exhaust stack installed.
I'm building one in my garage now, although my garage is far from clean and organized like yours (I still don't know where I'm going to put the Bridgeport). And now my cheapo welding table seems...inadequate.