What do you want? At the age of 30, you are old enough to decide for yourself.
Be a normal dispute can you show that you still think of him. If you put in a true conflict and contact your father's father, it's ok to have distance.
Of course. A tense relationship does not need other reasons / events that could aggravate the situation.
Yeah, still congratulate him simply, the situation is calmed soon
Yes, I would congratulate him for his birthday. Maybe that's the first step into a pronunciation and better ratio.
Yes, you should do that, because he is always your father.