Have you tried using elmers washable glue stick to match points up before you sew? I've never made a quilt as intricate as the one you're making, so can't say whether it will help you or not. But it's cheap and you really won't be any worse off if it doesn't work than you are now, so it's worth a try.
I made a quilt for my DGD that, no matter what I did, never matched up. I named it "The quilt from hell". I think she liked the name more than the quilt!