Yes, slowing down could be helpful to achieving your desired goal.
All of my comments are, of course, my opinion and will be in reference to you goal as I understand it. At the following link, you'll see a close-up image of the DD
kit to which you refer, taken from the DD
Can't get a good look at the value of the balance pot, but the value of the volume pot and tone controls are different from the original PAS. When you introduce changes, the sound can change and there could be other issues, for instance Audio Regenesis
discussed some of the technical effects from changing the original 250KΩ volume pot to a 100KΩ. I see this kind of kit as more appropriate for someone whose original tone pots are damaged, non-functioning or missing and
who is not particular about retaining originality. There isn't much more information on the website about how the DD
tone control circuit may function differently from the original and how the DD
kit is integrated into the circuit - would be helpful to see a schematic. Another consideration is that, AFAIK, there are no published specs for the preamp with this kit installed, and neither are there, AFAIK, any results from a disinterested lab analysis.
I've read a number of posts where folks have reported a significant improvement in sound quality by replacing the volume pot with a "better" pot or stepped attenuator. My own PAS improved when I went to a better volume pot. The nice thing about this is that you get an improvement in the sound quality while keeping the circuit design original. Lacking more details about the pots in the DD
kit, IMO they do not look like anything of standout quality. Audiophile-preferred upgrades to the original volume pot include Blue Alps, or a stepped attentuator, or something like the Noble brand pots (if you can still find them).
Sounds like one or more of your original tone control pots aren't working quite right. If you want to keep to the originality of the PAS, then you'd need to find exact replacements if they are even available (I kind of doubt it). If not, then the only option is to bypass them, which will clean up the sound (the bypass procedure also has the benefit of eliminating the DC offset at the main preamp outputs). Or, go with the DD
kit in spite of any open questions about it. I don't know where to get replacements for the original tone pots. Maybe @peterh can suggest where to look?