How to handle an obnoxious table guest?

I stayed with a family this past shabbos (Vayikra) who welcomed me into their modest home which they share with their six wonderful children. I am withholding their names because they are modest, they don't have internet access, and I don't want to say anything bad about them or allow readers to figure out who their other guest was. Suffice to say I hope I made a more favorable impression than this guy, whom we'll call Ned. Because that's the first name I thought of that is not actually his own.

I feel bad for Ned. He is an older single. I don't know if he's NBM (Never Been Married). He is short, overweight and a little funny-looking. I didn't ask him why he wore suspenders and a belt today. I'm tempted to infer he is bitter and angry despite coming off as somewhat friendly. The last time I visited and stayed with this family, he was there. That time, Ned was so angry at my host he got up from his seat and walked over to my host to yell at him about something my host repeated several times that he had absolutely no control over: while Ned was on vacation, someone removed some food of his from a common-area refrigerator at Ned's and my host's shul. Okay, a mild annoyance. But not a major grievance, not something to get worked up about, and not something to attack my host about! I told a confidante about this exchange, and she said, "I wouldn't invite him back." But my host is a mensch, and today, there was Ned. This time, my hosts explained they were leaving for an 18-hour drive next Monday morning, around 0600, giving themselves a spare 42 hours or so before yontif begins Wednesday evening. And Ned gave them a hard time about this, suggesting they weren't allowing enough time. Is he stupid, or does he just like bugging people? The other big topic of discussion, which Ned initiated, is that the power locks on his car weren't working. They would unlock, he claimed, without warning and with no provocation. After listening to his crap for much of my meal (which was delicious, BTW--thank you, Mrs. ----), this struck me as darkly hilarious. I helpfully tried to explain that the only likely fix was to replace the power locks, which would cost about $500. Ned demanded how I knew this, and I explained that when I visited a Carmax showroom, one of the advertised options for a used car is power lock installation, and that's the approximate cost. I then asked Ned how old his car was, because maybe it wasn't worth replacing the power locks. Ned refused to answer my question and sardonically asked if I drive a Lexus. (It's in the shop.) My host jumped in and helpfully suggested disconnecting the power from the power locks and just operating them manually. He was already annoyed because he had told Ned at least twice that discussing power locks at a shabbos table wasn't appropriate. Throughout these conversations, I discerned Ned is one of those guys to whom everything must be explained twice and slowly. We also discussed the Chicago grid system (address numbering) and how it is superior to Brooklyn's, and Ned said, "I don't know what you're talking about." Well, when you put it that way, I'm not going to take the time to explain it to you.

If Ned were 20, it would be nice for someone close to Ned to say, "Don't give your host a hard time about something that happened at his shul that he told you he had no control over; don't ask your hosts about their vacation timing since they didn't ask you for your opinion; and if your host suggests a topic is inappropriate, then just drop it." Ned is closer to 60, and if someone tried to help him like that, I suspect he wouldn't take the suggestions seriously.