I see a volume opcode there. Are you sure you commented out all those opcodes?
Frankly, the next thing I'd do is get a program that displays the midi messages your clavinola is outputting. I'd want to make sure the clavinola isn't outputting volume controller (7) messages with a really low value, or expression controller (11) likewise. I'd also want to check the velocity values on all the note-ons. When you play with medium (normal) force, those velocities should be around 64. Playing with full force should give you velocities over 115 (hopefully close to 127)..
I'm beginning to suspect maybe your keyboard is outputting very low velocity, even on the loudest notes. In an sfz with just one velocity layer (like Maestro, which btw is one of the better-sounding small pianos), it may not make a difference. In a sfz with multiple layers, a low velocity from the Clavinola may be limiting you to hearing only the lowest velocity layers.
If the problem is indeed the clavinola, I would first recommend replacing it. Other (less effective) solutions may be to use one of the volume-related opcodes listed in my previous post to compensate for the clavinola's low velocity. I'd start off first with amp_veltrack. This sets the overall "velocity sensitivity" for all midi notes. "Velocity sensitivity" is:
The difference in volume between your loud notes and your soft notes
If you set:
The difference between loud and soft is 0. In other words, no matter how soft or loud you play a note, the piano sound is always the same volume. I'd try this to see if the volume is at least acceptable. Assuming it is, now you just need to start increasing the sensitivity like so:
You'll start to hear more of a difference between loud and soft. As you try increasing values (100 is the highest -- it represents 100% or the greatest difference in volume), eventually you should arrive at an acceptable balance where even the clav's limited velocity range gives you an adequate dynamic range.
If you find that you can't dial in a value that gives you enough volume on the loud notes, while not too low volume on the soft notes, you could try using the 127 steps of the amp_velcurve_XXX opcodes. This allows you to construct 1 (and only 1) custom velocity curve for the sfz player itself. But you have to define 127 different opcodes (amp_velcurve_1 upto amp_velcurve_127) to individually set the velocity sensitivity of each of the 127 midi note velocities. So, you'll want to try amp_veltrack first.