Alberto, initially I had some problems getting the jaws "just so" bu now that I am more familiar with the vise it is simply not a problem for me anymore.

HMH uses the thread strength approach to the hook holding issue. (holding strength only needs to be greater that the force required to break tying threads; not the hook or vise breaking strength) Does the hook move while you are tying or when you are trying to move it with your hand? Make sure you look over the booklet that came with the vise to ensure that you are correctly positioning the hook in the vise and have the tension adjustments figured out.

The lever does have a "flat spot" designed into it so there is a little more resistance at that point but it is there to help "lock" the lever down. If you really have to strain to push down the lever the jaws are set too tight. Back off the tension ring a smidge and try it again.

Still a great vise IMO
------------------
Let it go and let it grow.