maths help please

so this is just our starting equation. F is villain's fold percentage, and y is the equity of the worst hand in our shoving range.

First it looks to me that there is a problem with your original equation. If I understand correctly, the pot before your play is 36.5. You shove your remaining 90. If villain calls, your equity is y (mind that this is your equity against his calling range). Let's look at what can happen:
- villain folds, your profit is 36.5
- villain calls and you win, your profit is 90+36.5=126.5
- villain calls and you loose, your loss is 90

So the equation should be:
0=F(36.5) + (1-F)(y)(126.5) + (1-F)(1-y)(-90)

No?

Let's first fix that, then we'll look at the rest.