I think almost everyone will develop a love/hate relationship with stims if they consume long and regularly enough - every single person I have ever met who fits that cetegory has done. Ever wonder why you hardly meet an aged speed freak? They're either dead or have quit.
This is classic overoptimistic thinking that occurs when we are at the tipping point when use becomes problematic.
Here's the news brother - you already know it but you won't want to hear it, but I'm still gonna tell

The thought that its "not causing me any real problems" is straight up denial. It's already problematic and will soon hit a steep incline in that.
It prevents you working on your PhD - you are already fully aware that you "hate it" and that it has "its claws" in you and that you "don't really want to spend the next 20 years or however long as a professional meth user " That kinda realisation doesn't really sit easily next to your musing that its' "50-50" which way it will go and that there's a "career in meth" consideration!
You're a bright person. I'd hate to be reading here met year how you'd sacked your studies off to dive into a bag of meth - total waste