While attending a sporting event is not forbidden, JWs are told not to favour any particular team as that is considered a form of nationalism.
Well, see how you will get varying answers. I never heard of "not favour[ing] any particular team."
GO CUBS!!!
As far as "celebrating" Christmas or birthdays with family, it all depends on what you did and who knows what you did and what you say about it. JW's are against anything that is considered "interfaith" which includes stepping inside any church/temple and certainly includes putting up any holiday decorations on your home. But if you went on a tour that included the Vatican and weren't there for services, most JW elders would not care. I regularly went to family funerals and some weddings at churches, but did not mention it to other elders. I doubt they would have a big problem with that if they knew, but I figured I would not take that chance. I went to some birthday gatherings of family with the excuse of "time with family" but again did not tell others. But if a member was accused of "stumbling" another member by their attending or participating in any "interfaith" stuff, they could be brought before a judicial committee. And some local congregations could do this just from the very knowledge that a member attended, regardless of the fact that no other JW's were even aware of it, let alone crying that they were stumbled.
Pagan and magic stuff, mediums and psychics- absolute wrongs according to the rules. Any knowledge of any involvement for any reason would get a member investigated and probably in front of a judicial committee. If a member participated to any degree even as small as curiosity for fun, they better keep it to themselves.
Christian music- I suppose it all depends. JINGLE BELLS has absolutely nothing Christian or even Santa Claus related. It's about winter. But playing it in the car with a bunch of JW's will get you in hot water. Many Christian songs say nothing wrong, so maybe not so much of a problem as anything that people relate to Christmas. But certainly, JW's will get in trouble for sharing religion-laden songs with other JW's. I find that most people (myself included) would not recognize "Christian rock" if it was not obvious, and JW's could probably listen to it among others and nobody would care.