Just for fun I previously tested and was successful in
manually adding / "registering" SH_Integration on top of old, non-universal hotfix
on a PW1 with firmware 5.6.1.1. So it had scriptlets without using the new universal hotfix. I just took the Sh_integration binaries/.so files and handler registration commands from unpacked universal hotfix bin file and did things manually via SSH / USBNet
No idea it that would even work on Kindle Touch with fw 5.3.x (same for if "universal hotfix" would even install it and work correctly on that firmware). It certainly never was tested on such and old device and firmware.
And I also recall that I was successful in installing and using
"Kwordle" on that same PW1 And when someone else tried using it on Kindle Touch it wouldn't work/install because I guess there are some differences in structure of "appreg.db" database into which KWordle installer script tries to add stuff.
Since registering Sh_integration also needs to add various things into "appreg.db" I wouldn't be surprised it also errors out when tried on Kindle Touch & fw 5.3.x.
Does anyone know if support for "booklets" existed and worked on 5.3.x?

If they do work instead of trying to "retrofit" scriptlets support to Kindle Touch firmware you could possibly use KOL booklet for starting KOReader.
https://github.com/yparitcher/KUAL_Booklet