since your exhaust leak is on the manifold side of the CAT any exhaust leak is certainly coming into your cabin. doesn’t that worry you?
any patch you put on will flex off, and then you will have more mess to remove/ repair.
i can see doing a temp repair on the back part of a tail pipe, where the exhaust is already behind the passenger cabin, but an improperly repaired leak in front of you is tempting disaster.