Russell is capable of being civilised, look at what his work collegues have said. He's simply prone to outbursts, a wedding may leave him unhappy as he seems to dislike couples generally, but naturally we only have non-family couples to base that off of. He definitely believes he has claim on all women, but with her being family it may be different. The main cause of contention would be him and female guests at the wedding, as he notably has no respect for other couples and could definitely find himself in a tight spot if he decides to tell a taken woman how he's 'totally legalising brothels in Utah guise'.
Failing that, some bridesmaid will have to endure a speech about how much he goes to the gym and his work in law firms, then topped off with an attempt to seduce her with one of his many dance routines.
Read the transcript of the court case, Russell is meek and humble, despite his outrage post-case. Look at him in the interview with Fox News, if I told you that was from a normal court case that a rational person would file, his response would be pretty much what a normal person peeved that they lost a case would say. Russell is an internal guy, on the surface he will say he understands, nod his head and entertain a conversation, but internally he's changing events so he's the good guy. An example of this would be Farrah Abraham, threatened with a countersuit he drops the case, but just as he concedes that he has no case by dropping out, he makes up some story that she's begging him not to file it and like Caesar intervening at Brutus' execution, he mercifully forgives her.
The only exception to this is when he's angry, like when he lost his job and was upset that the smoker wasn't fired. He's certainly prone to these outbursts, but they require him to not be at a function, i.e; a court case or a wedding.
tl;dr: Russell isn't some massive spaz out in public, he's a keyboard warrior with limited anger management.
EDIT: Russ update, more Planet Fitness shit. At the end you can see he's on the elliptical.
