
That would have been scary to have it lift & fly with you in it. Sorry to hear of your sprain...
For the top roof where you have the tarp, I was going to suggest putting a pretty stiff wire up that would keep it from sagging due to rain. Maybe even hardware cloth only & remove the tarp completely when you have that type of wind? The chickens can "learn to stay" (some of mine do, some seem to like getting wet!) in the roost section to stay dry...
Or for weighted tie downs - buckets of cement or tires - that you can move each time you move the tractor. Yes, PITA, but more do-able than some other tie downs.
For next chicken tractor - maybe something smaller & only for night time cooping & then free ranging in "hot" poultry netting such as the "permaculture peeps" use... Several different lower profile tractors/"coops" used by Justin Rhodes & Joel Salatin - you can google and search You Tube for lots of videos on the different styles they themselves and their many followers use.
Justin Rhodes has just given out the newest plans for his easily moveable "chicksaw 2.0", but at a projected $750 + for a new build, I won't be building it myself anytime soon... His holds around 30 chickens, I think, for night time cooping - they are out during the day in poultry netting.
I am looking at building several smaller CP hoop coops for my new tractors. They will only be 4' wide (the CP will be cut to 8' lengths instead of the 16' & 1 panel will then make a full coop). Can't walk into it, but could access both food & water from either end until they lay, then could put a nest box in one end. Different door options. All of my birds are really liking roosting way up high, so won't be happy with much lower roost that these will have but we shall see...