with a TT that size you should always use a wdh with sway control. ideally you want a wdh with integrated sway control as that TT is too big for friction sway bars. I'm guessing that the excursion's hitch states weight bearing limit is 500 lbs (class IV hitch). I'm guessing the F350 weight beating limit is 600 lbs (class v hitch). Your TT tongue weight will be significantly over those limits. The F350 will be fine with the TT, the ex will probably be ok with it but again use the proper equipment towing 1 mile or 1000 miles. Also make sure you have a proportional brake controller or an integrated brake controller not a time delay brake controller.
As for the AC. I have a smaller 13,500 btu single AC unit. It has held up during the heat of summer in NC, SC, and FL. It works hard and I get condensation on the windows but it kept my 30 ft TT cool. As I said above, go with the TT or 5er that works best for your needs and wants.
