Beautiful, eye catching colors! My suggestions:
1) Very narrow (1/2" to 3/4") black sashing between blocks.
2) Rotate blocks - have one heart with bottom towards bottom of quilt. Turn the block next to it so the bottom of the heart is towards the top of the quilt. Repeat across row. Next row, reverse the direction of hearts (if facing down, turn up, etc.).
3) Make a row of sideways hearts (points don't need to match in this row). Then a row of right side up hearts, a row of sideways hearts (going in opposite direction from first sideways row), then a row of upside down hearts. By using sideways rows, you can use the blocks where the points don't match. Each of the rows will be facing a different direction.
Just my humble 2 cents...I love your colors and the overall look of the quilt! It will end up fine, no matter what you decide to do.