I was told not to plant them more than an inch deep and to just make sure not to let water stand in the seeds (unfortunately, one of my three pots didn't do so well due to this).

I don't mean to sound discouraging, but I don't think T. fortunei (especially a mere seedling), will survive a winter in your zone. I doubt a mature fortunei will overwinter in a zone 5a without some heavy duty winter protection. Why not just grow it as a containerized palm. (PS. They are fairly easy from seed, don't plant more than 1/2 deep, keep slightly moist and use bottom heat if necessary.) Good luck!