I am of about the same experience as you, I have only four popper roasts to my name so far.... but a few things I have found.
If you have too few beans in the popper, the roast takes longer to heat up. I was doing about 3/4 of a cup at a time. Leave about 1/3 of the volume of the popping chamber for expansion of the bean. I assume this slows air flow, so the air is in contact with the heat element for longer.
The ambient temp really affects the roast, I had a breeze on one batch and couldnt get it to second crack. I blocked the breeze and things started moving again. Having said that, 14 deg doesnt sound too unlike what I would have been roasting in. You see quite a few people roasting within a cardboard box (top open), so that might be worth a go.
Have a look on youtube, try a few different searches. I found a few that were helpful.