I'm not much of a Drosera expert but from my understanding their ideal conditions are similar to a venus flytrap's.
Lots of sunlight - direct / indirect depending on species. I have a Capensis, Nidiformis, and Capillaris sitting outside in full sun thriving. I'm not sure about your spatulata. Try indirect or partially shaded sunlight for now. Give it a decent photoperiod (at least 6 hours). Most of the time when sundews are in direct sunlight, they don't exhibit much dew because most of the moisture is evaporating. You're more likely to see dew in the early morning, around sunset, or in the shade.
Water - I use the tray method but I don't keep them waterlogged. I treat them like a VFT; the soil should be moist to the touch in that if you do touch the soil, a few particles of peat moss should stick to your finger.
Humidity - not a huge issue IMO. But then again I live in NYC, where summers are naturally humid. I think as long as humidity isn't below 30%, you should be alright.
soil - it looks like you have soil down right. 50/50 ish perlite / peat moss.
Based on your post though, it sounds like you're moving your plants around a lot? Try to keep them in the same spot that gives it consistent light each day. Moving the pot to different spots may confuse the plant and/or stress it, thus reducing dew output.
Other than that, I suppose just give it time. Where do you live? Some sundews prefer mild temperatures and will produce much more dew within that ideal range. I've seen my capillaris and capensis produce a lot more dew on a 65-75 degree day compared to a 88-93 degree day.
Dew droplets don't get extremely huge, but they're noticeable. I'd guesstimate about 1-2mm diameter for a full dewdrop.
Like I said though, I'm no expert on this stuff. Most of what I know and told you came from what I've read on sundews in the past. One of my major sources is this site:
Perhaps it can help you a lot more than I can.