Whether Saavik was half-Vulcan/half-Romulan or full-Vulcan, she was raised on Vulcan as a Vulcan, just as Spock was. Even as a full-Vulcan, I had no problem with her crying. Whether they admit it or not, Vulcans -DO- have emotions.
But you said Barex is full-Romulan, and I took it as being implied that he was born/raise in the Romulan Empire and served in the Romulan military on cross-duty assignment to Star Fleet, much like Riker served (briefly) on a Klingon ship. But let's say that he was somehow adopted by a Vulcan family and raised on Vulcan, that doesn't change the fact that he is a Romulan and therefore should NOT have any mind-meld abilities. However, comma, that would imply that he is serving under false-pretenses as a Vulcan but in fact is not. Star Fleet would not, at this point in history, allow a Romulan, even one raised on Vulcan, to serve. And he'd never pass the physical as a Vulcan. Yes, Saavik got away with it, but she was half-Vulcan and also had Spock vouch for her (in one of the books, he put his reputation on the line to get her into the Academy). I might buy that Barex was able to learn, after a fashion, how to do the neck pinch thing. EDIT: In the dialog, Barex openly admits to being a Romulan.
As to plot holes ... there's too many things that happen without explanation, such as Zeta capturing Jansen or even that Zeta controls the K-computer, and the whole mental flashback thing was totally confusing as to what was happening. A lot of that had to do with the limitations you put upon yourself by writing in script-format. You also limited yourself by restricting your cast to the eight senior staff. In a real military setting, the neither the Captain nor the XO would not beam down to a potential combat zone, but rather they'd have a mid-tier officer in charge. I can forgive this, however, because this policy was set as canon in TOS and TNG (sigh).