Word for resetting or recalibrating

Why not settle for changed which, as it turns out, is the stock word in such contexts?

transmuted and toned down are other alternatives you might like, but the former could sound a tad heavy in such a context.

As regards your sentence, I suggest that you rewrite it because it contains a dangling participle. It appears as if the party incident has spent years of chummy relationship with your boss. Thus perhaps, you could write—

After years of a chummy relationship with my boss, I was forced to change our relationship into a formal one owing to the party incident.

I was forced to tone down the chummy relationship with my boss,thanks to the party incident.

EDIT— In response to the OP's comments, I am slightly expanding my answer. Since the OP wants the sentence to conjure in readers a sense of "quantifiable relationship", if you will, I suggest the phrasal verb ratchet down, which readily evokes this sense (ratchet, by the way, consists of a toothed wheel and a bar which governs motion; the phrasal verb furnishes the notion of metaphorical motion).

As regards the other query, spending for some reason didn't seem to sit well there. I may be wrong on this count but would certainly, either leave the word out or use enjoy instead because it collocates fluidly with chummy relationship.