It could also be that you're not dithering often enough. Dithering every 30 mins means you're taking 180 frames before each dither and that'll really let the walking/raining noise build up. you could try doing 30" subs and then dithering every ~10 minutes if that's practical? For me personally I dither after a max of 5 subs (or dither after a sequence of something like LLLLRRGGBB) , but I know I'm also taking longer exposures and have the benefit of automation.
Personally I've never used a GTi or Lumix camera, but if you're able to hook them to a computer with NINA, there is an option to have it dither automatically even without an autoguider
Few hundred pixels is definitely enough, and kinda overkill (mine goes a few dozen). I think the frequency of the dithers is probably the main thing that could help with the noise