Okay, it is very late at night, but I think I now have a solution to
the last point, the one that involves TCustomDbGrid.UpdateActive.

The issue that remained was that the connection between the DBGrid and
the TTable was lost under certain circumstances.

I have put the following into the DBGrid's OnResize() event handler:

DBGrid1.refresh;
Table1.refresh;

That together with the source code changes discussed earlier seems to
solve the problems.