Speaking as, again, kind of a quixotic Zen Buddhist…
I don’t think the question really matters to me–I mean that in the purest soft agnostic sense. If and when the influence of a God appears, it’s as much a relevant influence as that of the ground or a tree or whatever. And if God has no physical or spiritual contact with me, nor I with God, then almost by definition I shouldn’t concern myself with it, as Zen Buddhism is about direct experience and awareness of the world and that which is in it.
I go semi-regularly, and every few years I try to go to a retreat. Essentially the weekly meetings are closer to a philosophy debate with a cool TA than anything else–basically, the master answering questions and occasionally offering some random bit of wisdom or an observation as needed to keep the conversation going. The longer retreats are much more structured, and include a lot of disciplined meditation both sitting and walking, lectures, chores, regimented meals and sleep schedules, etc.
I don’t–I celebrate whatever holidays anyone else in my group of friends or family is celebrating, solely for the joy of it.
I am not a vegetarian. Strictly speaking I should be, but I’m not at that point in my monastic life yet where that’s the biggest thing I have to worry about. I drink alcohol in moderation.
As far as I’m concerned, “sexual misconduct” is defined entirely as “has someone been hurt”. This sets me apart from a lot of old-school Buddhists but it’s not that uncommon a view among the modern set. As long as you’re acting in moderation, not increasing the amount of suffering in the world, and not becoming attached to it (in the specific Buddhist meaning of the word–that is, attachment is “will you be distressed when it’s gone”), it’s all fair game in my book. Certainly certain types of sexual conduct (careless, mostly) have a greater potential for harm or misuse, but I don’t see a need to prescribe.
Just about anything Robert Aitken wrote will be very accessible to a native-born American while giving the full flavor of Buddhism. “Zen Master Raven” in particular is a cute and easily-digestible introduction that nonetheless manages to tackle serious issues with its cute animal motif. If you feel comfortable diving in further, “Gateless Gate” in any number of editions is the traditional “beginner” book of koans and meditations.