I'll second Ross's comments, all very good advice & as he says, this can all get really expensive very quickly....
I think how you are progressing at present is just fine; you can spend all you want on different cameras, this filter, that gadget or whatever & not necessarily make any huge leap in quality of image necessarily....
The biggest challenge you face at present is a non-tracking telescope... doesn't matter if it's a dob, refractor, SCT or whatever... you are going to experience difficulties obtaining razor sharp images no matter what camera you use or what method you use for capture.
However, that doesn't mean you should abandon what you are doing as hopeless, you are producing some images & I imagine, are quite pleased with what you have accomplished so far (as you should be). Each image you have posted is better than the last one so, you are making progress which is great.
I don't know which 'holder' you were referring to but, you may wish to consider something like this:
https://www.bintel.com.au/product/or...v=6cc98ba2045f
Although, not necessarily this one... have a look on eBay, they can be obtained for considerably less money. You may find this assists you in managing your camera & your mount by freeing up a hand...
Something else you might try is zooming in the image on your camera to try & get a sharper focus perhaps; you could try using a bhatinov mask on a bright star to use the spikes it produces to adjust focus but, this may prove a lot trickier when you are trying to manage a non-tracking mount & afocal imaging so, might not be beneficial to you... If you are interested in giving a bhatinov mask a go, have a look on eBay, there is a chap in Melbourne who 3d prints them & they cost between $12 - $16 posted which is pretty cheap compared to those commercially available.
I would just keep persisting with what you are doing & keep looking to refine how you are doing things; experiment a little, try different things, you will soon see whether they help or not... You will ultimately reach the limits of what you can achieve with a non-tracking mount & afocal imaging but, wait til you've travelled along the path a little further, decide what standard of images you are happy with (or not) & then, whether you want to take it further & in what direction. When you have reached that decision point, then you start asking questions about what do you need to get to next level.. & it's probably going to start with at the very least a tracking mount possibly even heading down the Equatorial mount road, depending on what you want to do...
Again, I think you are doing quite well with what you have & I would encourage you to keep going with what you have, keep posting your images & just push it as far as you can go with what you have...
Cheers