I'm not sure about your relationship with your family, but if there are ever "remarks" made from Fundies in my husband's extended family or friends, I just make a very firm and non-violent return. For example, I attended my SO's friend's baptism, and the friend and his mom were singing to the church songs. I'll move with them and all, but I won't sing words I don't believe in. They were harassing me to sing, until finally I said, firmly, "I'm not singing what I don't believe." Now, in a church situation where everyone is having a good time, that will shut most people up. In a room of family, it will just cause chaos if your family doesn't already know your beliefs. When asked about no Xmas tree, perhaps say, "We're just not sure that the symbolism feels right this year," and leave it at that. If they press further, say you are studying further into these matters but have not come to your conclusion, and so don't feel comfortable discussing it. You can say that to most hard questions. "Until I find my place on that, I don't feel comfortable discussing it," or if you know your place, "I'm not comfortable discussing this."
Honestly, if things get heated, it IS your home. If one of your family members decides to push and prod and start criticizing, be up front and true to yourself. "I respect your feelings on the matter; however, in my home, you may respect mine, keep your mouth shut (or opinions to yourself), or get out," should work nicely.
Again, I'm not sure how your family operates. I'm OK with telling family to get out of my house if they disrespect my religion, food choices, or career. I will always create a loving and appreciative atmosphere for them, and will not openly criticize; I sort of demand the same. After a few initial "words" when many relationships started, they have learned to keep criticisms to themselves if they are not willing to learn about my choices before they judge and go on their soapbox. If you're not comfortable with that, make a list of potential questions they might ask, and your responses. It's probably quite unlikely they will even get asked, but it's great for peace of mind. Try to have answers that are true to you but not upsetting to a Fundy. For example, when asked if I believe in Jesus as a saviour, I say, "Yes I believe in Jesus. Great guy." That is true to me. If I said, "Yes," that would mean I believed in him as my saviour, but I repeated the part of their question that I could say yes to. I don't know about you, but I can't lie to people, especially about me and my religion. My words jumble. It just tastes bad.
Hope that help a bit. If you have something more specific we can try to help best we can.
Crazy Healer Lady
Health and happiness to you!
The purpose of a relationship is not to have another who might complete you, but to have another with whom you might share your completeness. -CWG