I also have to say I don't worry about matching stripes....I just go with however they turn out..I love striped fabric and I think I wouldn't if I worried about matching everything up nicely..I just love the texture it adds to my finished product. I think you shoudl continue on with your blocks..they are darling!
As far as half square triangles I think there are so mnay tricks to them that make them easier to deal with.
There are several ways...
Tube quilting
thangles
special rulers....I think you just have to decide what works for you..try a few out.