Here is the area.

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Need to see a pic, but I would first bring in an arborist and see if the cherry tree can be trimmed/shaped so that it is more appealing.
Instead of hiding your windows and house with bushes & trees, have you considered window treatments that will allow you to control the light and privacy?

Usually a neglected weeping cherry is beyond redemption - too many disease issues, too many graft failures. Not worth the effort for two weeks of flowers :-)

The type of hydrangeas trained into tree forms are paniculatas (eg. PeeGee) - these are the most sun tolerant of all the hydrangeas and flowering will be greatly reduced if in too much shade.

I'd look at a standard (tree form) dappled willow - Salix integra 'Hakuro Nikishi' - or a dwarf Japanese maple. There are dozens that will stay within your height requirements (would it hurt to get taller?), they appreciate shade and most have a very sculptural form that makes an attractive visual screen.