VMware Snapshot removal

Dear,

      I have a mail server hosted in on VM 5.5 which have a thin allocated space of 800GB and have around 1TB total space of storage .
      Now there is no space left on datastore and we added 200GB to make the server up.We tried consolidation but failed due to lack of space.Tried deleting all snapshots but delta files are still present in backend and growing big.
      Tried contacting support and they are recommending to power off the machine and consolidate which is a big problem as this is a live mail server and cannot afford long downtime.
      I have some doubts regarding this which I hope you people can help.
      1-If I try to clone this to a new datastore with 500Gb (actual server utility is less than 200GB), whether it will hang again as I heard it will automatically consolidate while cloning.
      2-Whether we require the full current storage size in the new datastore for cloning.
      3-How much time it will take if we are going for power off and consolidate this datastore.
      4-If we try to clone while VM is  powered on, whether it will make more size or make issues in consolidation for cloning.
Is there any other suggestions so that we can remove the delta files(we dont require any snapshots) and make the VM work fine.

Awaiting for responses :)