If it was down to me, I would be to dump the bitch. Install wall, ceiling and floor sound insulation and turn the whole pad into a rock palace.
...But it's too late now, you're married, if you do that you'll loose the house and the guitars
So you must accept that what she says is the law.
Do you have enough space where the wardrobe is, along one wall to build a fitted wardrobe and nominate half each, put you Marshall Stack and guitars in your half and her shoes in the other. Tell her you are fed up with your guitars cluttering the place up and you'd like to build a cubby hole for them, which would double up as a wardrobe at the same time.

Although you know it won't work longterm because her shoes are more important than your guitars. It's the law.
What are the people like below/above...If they live in a rock palace, could you maybe build a trapdoor and store your stuff there?