It has only been a few days since his wife's suicide, and yet when Wilson visits her grave, it is already covered in grass and blends into the cemetery. There should be a fresh mound of dirt, as is common, to let the ground settle.
When Wilson goes into the garage, his wife's car is still there. He looks down at the exhaust pipe to see it has been stuffed with rags. This was her apparent method of suicide. However, blocking the tailpipe of a car won't cause a backup of fumes. The engine will not start when the tailpipe is blocked.
It has only been several days since Wilson's wife committed suicide. However, his boss makes it known she is interested in him romantically. This would be a total breach of both common sense and normal social etiquette to approach a person who is grieving, in such a manner.