Read the second post at the top of the thread, it explains succinctly how audio FX plugins *do not receive* MIDI. The *only* way to use MIDI control for something like Amplitube is to use it in the MIDI FX configuration, or to use Logic's controller assignments (smart controls uses the same mechanic) to map an incoming MIDI message directly to a plugin parameter.
Because audio FX plugins *do not receive MIDI* in Logic, as per above.
Same reason. You can't use this mechanic - pretty much all of this is explained above in the thread. Give it a reread, and if there is anything you don't get, I'm happy to clarify.
Because you've probably already mapped this incoming MIDI message to a plugin parameter via controller assignments, which is why that message is "stolen" and you won't see it arrive at the sequencer (hence, no display in the transport bar).
See above. 🙂
Everything about this is contained in the thread. MIDI isn't mysterious, but Logic's behaviour can be complex depending on what you want to do, so some of this stuff isn't obvious - which is why this thread exists, really...