I think you're right about the clay pots. I purchased them because it seems like they are 'the' thing to use when container gardening, even though they do dry out so easily. I don't get why they are so popular.
I do organic gardening, so I can't mimic your method for success, but I can try putting them out earlier. I just got a grow light system today for Christmas
, not to mention that if this crazy warm weather keeps up, I can start my seeds in April, like you, instead of May.