Your file sizes have been just fine for DCM. Please don't feel you have to compress your files more to make things easier on our side.
Max cbz file sizes are encouraged to be around 175MB but can go up to 200 if needed. Bigger than that we suggest breaking a book into two parts.
I checked extensively for any compression artifacts and could not find any. JPG compression typically shows artifacts in high contrast or fine detail areas, such as black title lettering against a yellow background. Due to the nature of the original printing process, the high resolution used and the aging of the source material, these are medium contrast images at best, allowing the great compression ratio.
There is some black ink shadowing in the images which I confirmed to be in the original print using 3.5x magnifiers.
I will continue to check compressed images for any degradation before posting.