Regarding the lack of forehead ridges, Did Ambassador Nanclus have the ridges in TUC? It seems like the only times I've seen ridges on Romulans is TNG-era and after (TV & Movies, including Enterprise).
(this is total speculation now, but...) Could this have been sort of a carryover from the ridge-less TOS Romulans ("Balance of Terror")? with TNG on the air at this point it may have been an intention to differentiate TOS Romulans from TNG Rolumans (of course, I'm in no way an informed insider...hell, I'm hardly an outsider).
If that were the case, then the ridged Rom's in ENT just screw everything up (but it wouldn't be the first time ENT screws with something, now would it?)
just a thought or two...