The left and right speaker issue is a bit more complex. The program I use to edit may have full mixing capabilities, but recording software doesn't. I'll look into this in the future, but unlike the other two, there doesn't seem to be an easy solution to this problem. Manually overlaying the audio also presents issues.
I'm not sure what software you are using, but I know Garage Band has an easy button (edit: Looks like I was talking out of my ass. It's not that easy in GB, but it is possible. Just tested it for myself) for centering all voices in a Podcast, and I could only guess that other editing software would have similar features. I'm not sure how this would work with your recording program, though. If it's not doable, then I'd highly suggest you change your recording software. Sadly, I think I won't be able to listen to another episode until this is solved. It really put a lot of strain on my ears, and my commute to work is the only time I get to listen to the variety of podcasts I subscribe to, so I am limited to using earphones. I'm not sure what everyone else out there uses when making their podcasts, but this is the only one of the seven I listen to that has this issue. Good luck, though. Really hoping it can be changed easily.
Edit: Just to let you know, I was able to edit the file myself to get it sounding better. I exported the mp3 twice, once with the balance all the way to the left, and once with the balance all the way to the right (mono sound for each case). Then, I was able to import the files again back into my program, and voila, I had two channels both playing together and with balanced sound. I did all this on OSX using Garage Band and iTunes. It took maybe 10 minutes tops. The process is a little more detailed than I've let on, and I just left out specifics because I know few people here use Macs, so I didn't want to waste my time (assuming you are using Windows software).