With most scene I actually recommend baked lighting as you get more from that that than you necessarily would with dynamic lighting. I don’t always recommend it for most who have said they’re using Dynamic lighting because at that point most have made up their mind and don’t want to deal with the creation of lightmaps.
To get more bounce light in your scene you can go into the World Settings > Lightmass > Num of Indirect Lighting Bounces. By default it is set to 3. You can change this value manually by typing in the number you would like.
This is also on our lighting guide: A new, community-hosted Unreal Engine Wiki - Announcements - Epic Developer Community Forums
Adjusting the Environment Color here as well will determine the color of the shadows that are baked. Using a value lighter than black can get your lighter shadowing as well.
For the square window image issue, what is the lightmap resolution of the wall where the shadow is being cast? You may just need to increase this if it’s too low.