I don't think the way the skimmer is turned will make a lot of difference. As long as your pump for the skimmer can pull water you should be fine. For the skimmer section I would make that baffle 12" tall and make a stand out of eggcrate and pvc
to raise the skimmer to the height it needs to be to be in 8" of water. (about 4")
I would make the return area as large as you can stand it to be. If you have too small of a return then evaporation is going to be a problem and you will have to top off a lot.
You will need to determine the working level of the return, the amount of water needed to keep the pump submerged and the amount of room left to allow for a power outage or just having the pump off.
How long is the 30g tank?