Thanks for your insightful questions. I'll try to answer them.
There is certainly substantial support. Whether it is majority or even needs to be is unknown. Plenty of revolutions are carried out by only a small minority of people. Most are passive.
2 & 3) Iran was a fairly free country before 1979. It is not some Arab dictatorship. The Persian People have a 3000 year old history (& close relationship with the Jewish People). Put simply and a bit crudely, the Iranians are smart, civilised and sophisticated people, quite unlike what the US was mostly dealing with in Iraq & Afghanistan (stupid, ignorant, inbred tribalist goat-fuckers).
Also, the US has been very clear that this is not a "nation building" exercise. This is about breaking things & taking out the bad guys until someone half decent arises.
A land invasion would be "to enter Tehran, overthrow the Islamist regime and install a friendly regime and then leave."
No democracy or nation building. Just making sure the bad guys are dead and someone rational (not a crazy Twelver Shia Islamist) takes charge.
RE: Israeli Ground Invasion of Iran - An Available Option