Thesis length answers? I'll give it a quick stab!
"Do you think any of these things could be said for land based air power?" Pretty much all of them. Land based Air Power tends to operate from non-mobile bases whose locations are well known and plotted decades in advance. Most lack any point defence missile capability, and have nothing even remotely duplicating the defences of a Carrier Battle Group in their vicinity.
"Do you think nuclear deterrence might work?" Any country that fires a nuclear weapon at the warships of a country which is nuclear armed like the UK is inviting their own destruction. That is how deterrence works. You fire just one, we take the gloves off. To do otherwise would mean a loss of face (by us) greater than if we hadn't responded to the Argentine Invasion of the Falklands. You either back up your promises/threats or you are done.
"Do you think tactical/ballistic missiles might be countered by our own weapons?" Theatre BMD is a developing capability within the RN at least, SAMPSON can do it, Sea Viper will do it and the T45s will have their engineering problems sorted before it truly becomes necessary.
"Do you think there might be non nuclear adversaries?" Most of the world falls into this category.
"Overall, my opinion is that they are the wrong ships for the RN." Tough. We are getting them. The time to whine about it is over and the time to make them the best ships we can is here.