Congrats! and welcome back
to try to answer your questions
1) Yes, your salt will temporarily buffer the water when the water is just mixed or after waterchanges but for longterm buffering without substrate, you will need to test the levels and add buffers as needed.
2) IMHO, your skimmer is not that good, if you can afford it, think about upgrading it. As for the immediate problem, try adjusting the valve on the intake to pump less water. Skimmers can also pump excessive bubbles when certain things are added to the tank, water conditioners, meds, foods, even your hands in the tank can cause a skimmer to bubble excessively. Either way, It will not harm the fish.
3) A clownfish is a great starting fish but IMO, I would leave the anenome out for several reasons. Firstly, you still have a relatively new tank where water conditions can rapidly change....an anenome needs a more mature tank where stability is key. Secondly, you do not have enough light, not by a longshot. You will need to upgrade to T5's, PC's or even halides. For your tank, a min of 150 - 175watts 50/50 IMO. The clownfish will do just fine without an anenome...it is not cruel, you may even find the clown will host in an empty shell or cave in the rockwork.
4) As for a pump, it depends what you use as a top off container and where you place it in relation to your main tank. If the pump has to pump water up (head), then you will need a larger pump. If the head is low, a smaller/cheaper pump will do just fine. In my own setup at home, I use 20 gallon plastic garbage containers which are in my laundry room and I have a medium sized Mag pump that pumps the water all the way to the living room with 3/4" tubing. Not super cheap(about $130) but super convenient.
5)If you are not using substrate, I would also pic up a calcium and GH/KH hardness kit. MAke sure you have 0 nitrItes before you add fish...nitrAtes are ok as long as they stay low.
good luck