[name_m]Welcome[/name_m] back and congrats on baby #4[name_f][/name_f]! We have very similar styles/preferences, so hopefully some of my thoughts are helpful.
[name_f][/name_f][name_m]Peter[/name_m] is a personal favorite, and I love it for many of the reasons you listed. Nicknames are quite a challenge, but it sounds like you’re master nicknamers and something will come along organically regardless. [name_f]Love[/name_f] the suggestion of [name_m]Pio[/name_m] and maybe you could throw in an “I” middle name? [name_m]Or[/name_m] maybe [name_m]Poe[/name_m]?
[name_f][/name_f][name_m]Ephraim[/name_m] is also on my list, though I do sometimes struggle with its pronunciation/spelling ambiguity. [name_m]Remy[/name_m] is also a fabulous nickname, though has quite different vibe than [name_m]Ephraim[/name_m] (more suave and modern). M0rris and [name_m]Ephraim[/name_m] are quite “Jewish grandpa” together, but it doesn’t strike me as unusable for non-Jews.
[name_f][/name_f]Also, FWIW, I actually prefer [name_m]Peter[/name_m] with your last name!
[name_f][/name_f]Based on your writeup, it does sound as if [name_m]Ephraim[/name_m] is your preference right now. I do sometimes hesitate on dark horse candidates this late in the game though, and would ultimately prefer a name I’d always loved (i.e. Peter).