Since you have already cut your pieces, you will know to starch next time. Smiles.
I do have to agree with SQ, your best bet is to construct your block from the 4patch out, eliminating the need to even make those difficult pieces you are having so much trouble with.
Each time you are making the square larger by adding triangles to the straight edges. This gives you a bigger square with straight edges to work with for the next step, which is adding larger triangles.
The trickiest thing you have to do is sew two triangles together to make the larger triangle on some sections. Try it this way just once and you will have your 7 blocks done in not time at all.
Smiles and hugggggggs,