For game like that, I'll choose using shadow mapping shader or just stencil shadow with dynamic lights. That will give almost the same result.

or maybe I should divide level into several parts, interiors and exterior separated

If you don't want to do lightmapping, you may adjust the ambient of the model in its action.
This way you can solve the problem of brighter models, but not partial lightning.

jop, i solved it similar way. but i also realized that it wont work as i first thought so i made one level for upfloor and one for down floor. simple and effective