Trying to remove the bolts that are holding the tailpipe (what is left of it) on

Already used WD40 and nothing budging.
If worse comes to the worse, would it be ok to cut the bolts off?


Strange place where the tailpipe sheared off, but I must admit there is a noticeable shake in the back of the van when stationary, which seems to have shaken the weak part of the tailpipe loose. I found it basically hanging by a thin bit of metal so I helped it off!
Any ideas why the van shakes like this - is due to the exhaust itself?
Appreciate your help!