After going through the calculations and previous test simulations then something was bothering me. I could not get the pressure under control. So after studying more my data I found out that my pressure and thrust curves were inverted and this is wrong.

After careful modelling this is the new data I am using for the new test:

As you can see thrust and pressure are now much more better than in prev. test. This means slight changes in nozzle design and also propellant length and core diameter and core offset.

I'll prepare the new nozzle and propellant and hopefully can launch a new test in coming weekend.