Hawkmoon, you are a bright guy with loads of experience and a great physique to
prove it.
Lowering your protein . . . you won't notice a thing. Guaranteed if you stay within
the RDA. (I know people who have gained muscle on lot less protein.) And you will
feel better too.
I also suspect you are not in a growing faze, maintaining what you have being a
priority. (Think age, health.)
Personally, I would just eat a 'normal' diet, don't stress the protein, it will be what
it will be. But do keep track of the overall calories, just don't get fat unless you need
to (too lean).
This high protein obsession (not saying you) is just that . . . an obsession with no
real science supporting i.e. anything beyond the RDA. Just follow the RDA and you
are good to go. As you lose and gain muscle just adjust you protein in accordance
to your weight. Easy peasy.
Just my opinion.