I think you might not need the boning in the bodice, and twill would be a bit heavy for the lining. What I've generally seen for dresses of this era is a lightweight cotton lining, or doubled cotton net. Both options for closures seem equally plausible to me - it just depends which works better with your pieces.

Here are two patterns/descriptions that might help a bit - an evening dress (http://chapmanmuseum.pastperfect-online.com/30796cgi/mweb.exe?request=record;id=EB5B3148-D7D4-44BF-AF37-301938283709;type=101) from just before your period, and a wedding dress (http://chapmanmuseum.pastperfect-online.com/30796cgi/mweb.exe?request=record;id=EBA85E9C-C10A-4F03-B71A-325925769902;type=101) from 1916.