macbook pro - disable csrutil without recovery mode
You can't, and that's by design. If an attacker could disable system protection while the OS was booted it'd be pointless. If you find something, please file a radar because this is an important security component. Single user mode is the same as normal OSX just stopped a bit before a bunch of niceties load, so no dice there. You'll have to get into recovery mode somehow and if you can't even boot to single user recovery you might have a bigger issue than just GPUs. 

You could, potentially, boot using an eGPU if I understand the issue. Issue is an eGPU is hard to find and more expensive to buy than just fixing your laptop.