your quilt is just gorgeous! well done! i saw your update and am glad you figured out it was the seams causing your troubles and are having more success now.
i do a lot of handquilting. typically i use Quilter's Dream and it's very easy to quilt. I also use sharps - rather large but i don't know what size. I don't worry about the size of my stitches, partially because i tend to use variegated threads and figure i'm intending them to show. With practice my stitches have become very even in size and I like the look of the threads showing.
I have noticed that some threads "stick" and drag as I stitch, especially the thicker variegated ones. the project i just finished using a thick-ish thread kept having the batting pull through with the needle, making me say GRRR!
just a thought for your future project . . .
I tend to baste thoroughly and quilt without any frame, just over my lap and tucked under my legs. I did an entire queen-size quilt that way and it lays flat with no puckers or issues. For me it's easier than in a frame. I'm sure that's not for everyone, but it works for me.
have fun finishing your quilt. it is a beauty.