Your number are looking good so you are at a point of balancing the load and recoil function.
Yes the change in recoil spring weights to lesser weights would improve the function somewhat, just keep in mind that the pistol's slide has mass and the movement of that mass is what helps things to work. Slide velocity both rearward and foreward are balanced by the recoil spring system...too soft a spring my allow the slide to achieve too much rearward velocity and damage to occur (buffers were used in some guns to help with battering during this situation)
The longer case length of the 10mm already provides some lower numbers simply because of the space which there is no powder. Some powders are what they call position senitive if not held firmly against the primer flash holes. Generally the faster powders don't suffer from this as much.
What a learning process...Carry on have fun!
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