Such a load of questions.
I am not the be-all end-all answer guy but that said I do have some opinions.
I have been treating joinery at the time of cutting with a sealer of some kind. Any materials with a measurable thickness when installed need to be accommodated in layout. I prefer to seal end grain of green materials with something like anchor seal (wax emulsion which can discolor wood) but have also used the latex products used in the log building world and even water based poly. To aid assembly I like to use a finer wax (as Butcher's bowling alley wax) but have used parrafin and bar soap.
I also have been waxing pegs for assembly purposes but started out dipping in the common oil used to finish the frame. (linseed, tung, others, and combinations)
I would think that a mechanical connector should hold the brace while you skin. Perhaps we should talk to the engineer on this panel.
The panel manufacturers are the folks to discuss the necessity of strapping but I find personally feel that the strapping is a good place to stand when installing roofing. Strapping installed in two directions may seem excessive and paranoid but an airspace may have some value other than making it easier to get the snow off so the metal can go down. Try the SIPA web site for their suggestions.