As we shared our past fears, gradually, you felt closer to me.

If not:

As we shared our past fears gradually you felt closer to me.

Though technically:

As we shared our past fears, gradually, I felt closer to you.(the me infers 1st person, and you wouldn’t really know the other persons feelings)

(see how sarah enclosed her “however”?)

“As we shared our past fears, you gradually felt closer to me”

Since we have shared our past fears, You have gradually, felt closer to me!

But I feel this one would be the best and more of a proper way:

As time has gone by and we had openly shared our past fears, I feel you have gradually felt closer to me!

To make the sentence correct you need to have the tenses agree with each other. Since you said “shared our past fears” the sentence must be in past tense. That means the tense of “feel” must also be in past tense, making the correct word “felt.”

You wouldn’t say “As we are sharing our past fears you felt closer to me.” It sounds ridiculous for same reason where the tenses need to agree.

The second one does not make sense. You gradually were feeling to me? Do you mean feeling closer to me?

The first one, however, does make sense. Sounds good. And yes, the comma should be used after fears.

As we shared our past fears, gradually I felt closer to you.

Yes there should be a comma after “fears”.

How about, “As we shared our fears, I began to feel a closeness to you.”

Yes, you need the comma.

I hope that helps.