Whereas what you say is all relevant, I don't think you have adequately considered the other side of the equation, i.e. how bad can Coronavirus be?
Perhaps you are looking at the current 20,000 dead, most of whom are old and were not in the best of health anyway and therefore you are thinking that 20,000 is not that bad in the scheme of things and not worth the adverse consequences you outline? That would seem a reasonable position, logically if not morally.
But the 20,000 is probably nearer 30,000 in reality when we add in cases that have not been counted. And we haven't "finished" yet, not by a long chalk. People are still dying in their hundreds every day. I am guessing but it could easily be 40,000 by the time daily deaths are back down to a handful daily.
But here's the critical point. This (say) 40,000 is after all of the measures we HAVE been taking and with an NHS which has managed to cope. It is a tiny fraction of what woul have happened without such action.
Let's say the mortality rate is 0.7%, which seems quite a conservative figure but perhaps a realistic one. If we stop our social distancing and other measures then perhaps 50m catch this and the raw maths says 350,000 die. But it's much worse than that. Because we could not possibly cope with the numbers of ill people and would have nothing like the necessary ICU capacity needed. Most people needing ICU would not get it, so they would all die. The death rate would be much higher than 350,000. It could be half a million easily.
How can we possibly follow any course of action which could result in hundreds of thousands of avoidable deaths? We have no choice but to carry on with the current strategy of doing everything we can to get the infections under control and to use such measures as necessary to keep it under control until we have a vaccine. And as an absolute must, to keep the rates below the NHS capacity to cope, or else we have loved ones dying alone in corridors and that is unacceptable by any basic moral standards.