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?

Following Islam out of fear for Allah Ta'ala

Q: I follow Islam out of fear of hell and of Allah's wrath, not out of love for Him or a desire for paradise and I don't like Allah. For me he is something cruel entity but powerful because he is a creator or God. I always think he will be going to harm me and not going to benefit me and He never benefited me, as I said I follow Islam because of fear. I don't want His hell or paradise both, can I make dua for Allah to save me from his hell as well as his heaven?