Choosing a WDH and weight my trailer, please help.

You certainly don't need a Strait-Line for a trailer the size you have. I use a simple Reese trunnion bar WD hitch for towing my 19' Coachmen, no sway control. If you're convinced you do want sway control then a Fastway E2, whether round bar or trunnion style, will work just fine and include sway control as a function of it's design, no separate friction sway bar needed.