I would go for the 1 ounce so that you have plenty of beads and just in case you upgrade to a larger humi you will still have enough beads. Also, 65% is likely what you will want as your cigars will smoke better slightly dryer than 70%.

I wouldn't use the 50/50 solution unless you get you humidor before your beads. Then you will only add some of the solution to the green foam that comes with the humidifier and you will season the wood with the distilled water only.