For inf. items, you need to have at least two of the same items before it multiplies. As for non-usable items, if you have at least two of them, simply collect more or manual sort it and it will automatically have 99.
If you are using NVIDIA, just go to the NVIDIA control panel, Adjust desktop size and position. Then adjust the scaling mode to Full Screen, Perform Scaling to GPU and tick the Override the scaling mode set by games and programs. Don't forget to click Apply.