I think you need to isolate what sounds you are trying to fix. If the tapping noise is inside the dash (in the middle) start there and attempt to track down the noise by duplicating the circumstances (that cause the noise) with your head in the passenger foot well.
If your belt is squeaking/squealing, it could be the belt, the alternator or an idler pulley. You'll need to pull the belt off (inspect it) and inspect each pulley for wear (grinding sound or rough feel when turning).
If your motor/transmission mounts are worn out, replace them. Visually inspect them and if torn or worn out, time to replace them. Personally, I don't spray anything on my motor mounts, if they are worn out, I replace them as they are not all that expensive.
As far as a flywheel or flexplate, (personally) I've never seen one wear out. I have seen damage where a starter failed to retract and ground the teeth down, but that sound is an unique grinding sound (not a tapping sound).
You may have multiple problems with your car whereas there is no one fix. The tapping sound in the dash, may not be related to belt squeal under the hood.