Welcome to BPL, Gray.
Yep, for ~down~ fill and waterproof shell, FF is the ticket. And since this is a summer bag, down fill would be my choice for almost any climate. Unfortunately, not many quality options out there if you’re sure you want a waterproof shell.
The Nugget: for a 2lb bag in this temp range, made w/ the outdated generation of Primaloft (‘P. Sport’) and which requires their clunky proprietary pad, even $230 is a ripoff, considering how long you’ll likely remain happy with it. IMO of course! :^)
Do keep in mind that these waterproof fabrics, being heavier and having less drape than thinner, ultrabreathable fabrics, will not allow down fill to loft to its fullest capacity. So, if comparing relative temperature ratings according to fill wt, you might want to take that into account.
EDIT: Since breathability makes or breaks this kind of bag, I agree that eVent merits serious consideration (link to bpl article). There are few decent alternatives. Integral Designs offers arctic-class down bags in Pertex Endurance (same shell as Nugget), but not in their summer-weight Primaloft bags. However my ID bag was essentially made-to-order, so maybe you could ask them what they could do for you.