As to the other question, Agent, watch my answer cause me to be verbally stoned! But I do think you can be a Catholic and not be clear on the Assumption of Mary. Not every Catholic is free from all doubts whatsoever. I doubt if there is even one who is totally free of every possible doubt or concern about this or that doctrine.
So in my opinion, which is one of thousands, you can be a Catholic and have doubts.
This being said, a monseignor of my own parish, maybe two years ago, we were having a discussion about salvation, in his rectory office, and at one point he leaned over his desk toward me, a smile on his face, and said “I have news for you. Christ is going to save EVERYONE!” And he was delighted with this. I said, excuse me, but the Bible is quite clear that most will not in fact be saved, that the majority of people will not be saved, that Jesus spoke as much about hell as he did about heaven. That he warned that we would not enter the kingdom of heaven unless and until, etc etc our righteousness exceeds that of the Pharisees, etc…there are quite a few passages about salvation in the Bible, but this monseignor was convinced that ALL would be saved. Now, does this make him a non-Catholic? Of course not. Does it make him a mistaken Catholic? Yes.
So not all Catholics believe every single thing the Church teaches, down to every detail, or if they do, they certainly have their doubts but defer to the Magisterium of the Church.
So don’t be hard on yourself for having doubts about Mary’s Assumption. Learn all you can about it and seek to find out the Truth, here and elsewhere.
There are plenty of very knowledgeable people here who can help you explore this area.