Vinny,
I too dealt with most of your concerns.
First (the jib cars). It sounds like you have the old Seaway cars (like I did). They cleat easily with an upward pull and uncleat (ya right) with a downward snap. The problem is, the whole cleat moves on the spring and the process is difficult, to say the least - more like damn near impossible. I tried a few modifications with little success. Those cars are simply a flawed design. I replaced them with these (Hobie part #1075 - I think CatSailor sells them too)and I love them.
http://www.hobiecat.com/support/pdfs/34_35.pdfPitchpole/capsize. This problem is a little trickier because the H16 is so over-powered to begin with. But that is what makes the boat so fun and exciting. Certainly your weight distribution and technique is the real secret. However, I converted to a roller furling jib which allows me to reduce sail power quickly and easily - especially solo - both when the wind is too high, or when approaching a boat launch. I would highly recommend this upgrade and have zero regrets on its purchase.
4:1 blocks? You better change those before you rip your bicept from its insertion!
Hope this helps
Dave