I cannot say much about the misfire (spark plug?) and oil leak but if you spray a bit of silicone on the drive belt and all goes quiet for a few miles that will explain those noises. No big problem other than being annoying and not something to stop you using it. Hopefully it will be down to alignment and/or tension of the drive belt. At least you did make it home. I would like to make a long journey or two with my car but the reliability issues keep coming up to make me think again.
