there are no gaskets for the timing cover and sump, use silicone.
When you say you've put instant gasket on twice now does that mean you've just stuck it on the outside and not taken the sump/timing cover off and done it properly? If that's the case you'll never stop a leak.
Also, is the instant gasket RTV type silicone and not something like Hylomar (which isn't silicone)
Unless the faces are fcuked i wouldn't try flattening them, the silicone should take it up.