Celebrations and Customs

Muslim business using adverts with Christmas decorations and selling Christmas items

Q: 

1. Is it permissible for a Muslim business owner to promote his business using adverts with Christmas decorations? 

2. Can a Muslim businessman sell Christmas lights, trees, decorations, etc.? 

3. What is the ruling regarding a person decorating his business with Christmas lights, Santa Clause etc.?

Attending a birthday party

Q: I know birthdays are not halal but if a close person invites me, I need to go. So if I went to a birthday party where there is no music, only relatives and close friends, I will not eat the cake but it seems bad if I don't eat the food they ordered, so if I eat the food will it halal for me? Only to eat the food.

Pulling the wishbone on Thanksgiving

Q: There is a tradition on thanksgiving where 2 people pull the wishbone of a turkey and whoever is left with the bigger part of the bone that persons wish will come true. I know celebrating thanksgiving is not allowed and I know that only Allah grants things, but if I pull the wishbone with my cousin not with the intention of getting my wishes come true but with the intention of just having fun, is it kufr?

Celebrating birthdays

Q: If someone follows the opinion that celebrating birthdays is halaal as long as they are not extravagant and as long as they don't include something haraam, then if that person says happy birthday to non-Muslims who are celebrating it, are they still Muslim?

Because I've heard from people that if a Muslim participates in a kaafirs events then they have committed kufr (atleats that is what I understood) but what if that person thinks its ok to celebrate birthdays?