Here are 2 advices for you to get your MBs undercontrol: 1. Level the images so that you white is really white and your black is really black. In this case the images where already good on the black side, but the white had still a lot of noise it in. By adjusting the white spot you could have reduced file size probably a few KB per image. And leveling also is a big help to make your cleaning life easier. Here is a guide: https://ouo.io/VNs7qP
2. Don't save your Black and White images as png in RGB mode with 32-bit colordepth, if you do file size explodes. As you can see when you compare the size of the RAW around 518 MB with your 926 MB. Save it as grayscale with 8 bit colordepth. To change the color setting click on image, mode and grayscale in your image editor. Saving black and white images with a colodepth of 24bit or 32bit is just bit posing. There is no super or ultra black to unlock by doing so.
I've never seen or had interest in One Punch Man before the porn of this scarred cutie. It would be even better if he had darkeye bags but I can pretend.