1) assuming the A/P was also left engaged, would we get the flare/retard sequence? Given that the flare does not arm by 350' during normal 1-ch approaches I have previously done, I think not.
I have never tried it, and also have min A/P disconnect of 50/150'. I am not aware of any A/T disengage minima EXCEPT that it is not 'approved' to use A/T in manual flight, so ,ogically A/T should be removed at 50/150' at the latest. I am assured you get RETARD and some claim you will get a reduced FLARE although I personally doubt that. FLARE itself will NOT arm. I did raise a thread some years ago to ask but I think that one went off the rails also. I think teeth will be rattled on touchdown. Ask in the sim next time if you have a few spare minutes. NB I gather there is a single channel autoland option now available for the newer NGs?
2) if not what target would the A/T go for, the MCP speed all the way to touchdown, and if you (incorrectly) did not disengage it, it would disengage 2 secs after touchdown, is this correct?
See above. If RETARD failed, yes.
I would recommend you take further questions which are not really relevant to this thread elsewhere to avoid 'clutter' - and DC-ATE's advice is sound!