Your module bootstrap file must be in PHP. You can do whatever proxy calls you want in nodeJS between the PHP bootstrap file and your module, but the PHP server needs an entry point into your code.
If you’re building a SMART on FHIR app, that’s a different thing and you can use whatever you want to do that.
Either way, you’ll need to offer a whole lot more details about the problems you are running into before anyone can help you. If this is something you need to pay someone to help you, there are several people in the community who can offer you training.
Otherwise you’re going to need to be far more detailed in order to get any assistance.