I also like the idea of the spirit's nature AS A SPIRIT coming up inconveniently. For example, lies and oaths... It can't tell then or break them (at least, not without consequences so dire as to just make it deadly... I like the idea that the fae issue with iron has something to do with an ancient broken oath to iron, for example)...
That said, Nick is still mortal. I'd let him lie and break promises like anyone... Adamsk won't limit that, but he won't get it either... And may fly into a blind panic. If he could speak, it might go something like this:
"YOU SAID YOU'D BE AT THE PARTY. YOU PROMISED YOU'D BE ON TIME. ARE YOU TRYING TO GET US KILLED???"
"Umm. It was a lie... To make her feel better. I'll call and say I'm sick or something."
"WHAT? IF WE DON'T GO, SHE'LL HAVE POWER OVER US!!! SHE COULD KILL US WITH A THOUGHT! ohgodohgodohgod..."
But instead, he'll just feel blind panic, even aggression since everything that might keep him from honoring his word to the letter would be a threat.
Hell- it's simple to do, too- it's just a compel of his head roomate aspect.
As for thresholds... I think it would supress, not scrape off... After all, Dresden says all the time in the books that there's nothing stopping a Black Court Vamp from crossing a threshold, except that for them, leaving their power at the door is fatal. Theyd die, not bounce off.