The plans look good, probably over engineered but that's a whole lot better to do that than to go the other way and and be in structural trouble later.
Check the Dexter axle website for axle installation info, if I interpreted this info correctly,you need structural crossmembers at each set of spring hangers at the bottom of the frame to transfer/share the torsional loads to both frame rails when cornering (more axles=more resistance to turning the corner). I feel your pain with health issues, welding is definitely not lung friendly, but I continue to weld because I enjoy the challenge of fabricating my ideas, I've foud that a fan behind me blowing the fumes away and a good resperater really help. I replaced my chopsaw with a portaband hand held bandsaw to get away from the noise and wonderful smell of burning steel and abrasive wheel particles in the air, its a little slower,a lot more user friendly, you just have to take your time and concentrate on following the line. Anything that the portaband won't cut gets the 4" grinder with a thin 3/64" or1/16" thick cutoff wheel. Another option would be a small horizontal bandsaw with a small removable table to turn it into a verticle bandsaw to cut small pieces by hand. Something else that I learned from an oldtimer, cut,fit and tackweld everything in place and then hire a professional to weld everything solid, the time consuming (expensive) part of most steel work is getting everything laid out, cut, and fit level,square and plumb. A small 110v "suitcase" portable wirewelder is sufficient to tack everything in place for your pro, it would also be handy for adding a bracket here and there as you complete your buildup of the house. Did I mention that I am a big fan of used brandname tools, auctions and pawn shops.
Good Luck with getting framed.