The settings you are baking with are quite low. You’ll probably want to increase your direct and indirect sample counts (mostly the indirect one), as well as lightmap resolution and max lightmap size. Those blue and red artifacts on the wall are likely due to low sample count.
If you have a GPU, I suggest selecting the GPU lightmapper instead of CPU. It’s usually a lot faster.
The area around each light looks rather dim to me. Did you make sure to mark each light as Baked or Mixed mode, not Realtime?
Finally, I see you are using subtractive mode mixed lighting. Depending one what kind of platforms you are trying to support, you might want to evaluate if this is correct choice: Unity - Manual: Lighting Mode
Check out these 2 chapters in our troubleshooting guide for some more info: