Dyna-Gro is a fertilizer, I assume? I use Superthrive and a fertilizer both, together. Have not used Pro Tekt. I do use them weekly (and weakly) for 3 weeks, and then flush plants with plain water the last weekend each month (recommended to flush out excess fertilizer salts so they don't accumulate).
Yes, many orchids may slow down growth in the winter. Can't help on D. kingianum, sorry....but I would guess it is slowing down for a little rest in winter.
The brightness on the light is hard to judge over the computer of course, but generally, your window sounds pretty good to me. Not sure that 6 hours of fairly bright light is enough...how much total light do they get?
While many paphs have only one bloom, others are sequential bloomers or multis. Congrats!
Alcra Pacific Nova 'Butter Buds' is an intergeneric orchid in the oncidium family. It has a lot of miltonia clowesii in it, and a lot of brassia, and is pretty temperature tolerant. Gorw it like an oncidium (fairly bright light, more water than a catt...let it almost/just barely dry out), and it should be fine. I find the intergenerics are pretty easy growers.