Your mesh is too big/too complex. It needs to be split up into many pieces. Also, the Auto Flatten tool does not give good results, it is better to unwrap the lightmap UV yourself.
I’m not sure if there’s a setting for that, the effect is called color bleeding. It’s normal, because the material of an object reflects its color, and the white walls reflect all color so when white light bounces off something yellow it will reflect yellow color. Also, you need to increase your lightmap resolution, you can still see the shadows from the windows on the floor are very “blobby” which indicates that the resolution is not very high.
I can see a bit of the wood color reflecting on the wall, if you change the indirect lighting scale I think that will affect how the color bleeding will look, though it can affect some of the other lighting effects and rendering time as well.