How are you feeling now? Did you take methadone eventually?
The time interval between the last dose of full agonist opioid and first dose of buprenorphine is generally given as 24 hours, but with methadone you should have waited at least 48 hours before taking the first dose of buprenorphine even though your methadone dose was quite low. Also, it's best to start with 2 mg of bupe and if after 2 hours, you don't feel all right, take another 2 mg, and so on. If I were you, I would just wait it out and then adjust my buprenorphine dose.
I'm not sure if it's easier to quit buprenorphine than methadone, but in my personal opinion and experience buprenorphine is a much better maintenance drug. I myself quit methadone after 2.5 years spent on it, the withdrawals were hellish, actually not very far from benzodiazepine withdrawal with some crazy symptoms on top of regular opioid withdrawal, and 2-3 months after quitting methadone I started buprenorphine maintenance as I couldn't pull myself together and probably was suffering from PAWS at that point. It's hard to say now if it was a good decision. Anyway, as a maintenance opioid that I have to take every day, I'd choose buprenorphine over methadone any day as it's a drug you don't really feel much and can live a more or less normal life without feeling drugged and without feeling withdrawals. With methadone though after some time on it I was emotionless and cognitively impaired. The first few months on buprenorphine are great after years of being drugged with opioids, feeling hopeless and depressed, sadly, this initial kick doesn't last forever, but then it's still way better than methadone, I've been on it now for almost 5 years and thanks to it I went back to the university, started working in a lab, all that certainly wouldn't have been possible if I was still on methadone.