Is it sustainable to have a relationship where one boyfriend isn’t very sexually turned on by me and prefers to just jerk off by himself to gay (and even straight) porn (mostly without me knowing), while I get all my sexual drive from him?
Don't make an issue of such things. Instead tell him you approve of him jerking off and watching porn - with or without you. The two of you just have to accept each other’s peculiarities, share expenses and live peaceably together. By doing so you will indeed sustain your relationship.
If he can sustain a relationship based on platonic feelings then sure but that doesn't seem like most people. He'd also have to be ok with just jerking off to porn and not actually having sex. It sounds unlikely to be honest but maybe.
Don't make an issue of such things. Instead tell him you approve of him jerking off and watching porn - with or without you. The two of you just have to accept each other’s peculiarities, share expenses and live peaceably together. By doing so you will indeed sustain your relationship.
How long are you together? Is there any sexual activity between you two at all?
I agree with masturbation in a relationship, all good, but if one partner is left out totally and doesn't have his needs fulfilled, I'd say this calls for a talk about or maybe an open relationship if there is no sexual fun/satisfaction at all.