Can you be sent back from overseas early if you are considered high risk and are in the process of being MEB?

If the Military Treatment Facility (MTF) has the medical/behavior health services to support the issue (regardless of 'risk') they will probably not be sent back solely based on that criteria.
If a P3 is dropped, the SM is referred and accepted to a WTU (now SRU) then the Soldier will receive transfer orders. The unit the SM gets sent to is not based on HOR. It is based on MTF capabilities and capacity of the unit. The WTU is ratio based 1 squad leader to 10 Soldiers, so a SM cannot be sent where there isn't enough personnel to provide oversight.

The answer is the can, but they do not have to. It depends on many factors associated with the location and your condition. Closer to home is not usually an option as that technically requires the military to move you twice. As long as your care needs can be met at home station you wil likely remain there.

Your CofC can return you to your duty station for a choice of reasons. Though there are so many daily tasks that are low energy or low performance needed or low capability required to be done every day, there is almost never a good reason to send an able bodied SM home early from deployment. Better to put the SM with a bad back and broken leg at the DFAC headcount tasker then pull a mission ready one from a platoon each day.
If you are redeployed early, you will return to your assigned duty station. Be placed in the Rear D command and then if that CofC desires to transfer you to a on post WTU, that's a possibility.