Bridesmaids and no groomsmen

You can have them walk down one at a time. If you want, half of them can stand besides the groom and the other half can stand beside you, so that way it may look more "even."

Lots of people have uneven wedding parties all the time and it looks fine! I'd just let it be and not try to make it even "look" even

You can have them walk down one at a time, and since it's a church wedding they can sit in the first pew. This way they are still involved but you don't have to worry about the photos looking uneven.

Do you have any close men in your life like a best friend, brother, cousin, nephew etc that could stand on your fiance's side on the big day?

Yes, I understand that but they won't be for him. They'll be your party but just stand on his side for the sake of pictures.

My daughters were married in the Catholic church. Their wedding parties sat in the first pew. Any photos taken during the ceremony are definitely focused on you as the couple anyway, so I don't see anything wrong having them sit during the ceremony. Photos before/afterwards can be arranged any way you'd like.

Maybe you could have them walk down the aisle, but instead of stand by you they can sit in the second row (behind your immediate family).