Heat swings are totally normal. Don't bother to monitor the box temp during the seasoning process. Just let it run on 250 and don't worry about it. Three major things will create large temperature swings during the seasoning process. 1) An empty box. There is nothing in there to absorb the heat. 2) It's not seasoned yet. 3) Wood catching fire.
As your box becomes more seasoned, the heat swings will become less dramatic. Don't worry too much about what's going on with the smoke. Just let it run. If you've been fussing with the controller a lot, set it back to 250, and let it run a couple extra hours. It won't hurt it.
Keep in mind, temperature swings are totally normal with the analog controller, like the #1, or the non-D models. The temperature might swing as much as 20-30 degrees in either direction during a cook. That is no problem for BBQ at all (think about the temperature swings traditional BBQ has which are much larger, when loading new wood, opening the lid, etc). The controller is a rheostat and functions the same way as the oven in your kitchen, which heats to a temperature above your set temperature, then turns off until it reaches a temperature below your set temperature, then turns on again. You would drive yourself nuts if you monitored the temperature in your kitchen oven, yet it works fine for delicate cakes, etc.
I don't monitor the box temp in my #1 anymore. I monitored enough times to feel confident it averaged out to my set temp. Unless something seems wrong, I probably won't bother. You can monitor the box temp during your first several smokes, just to see that it approximately averages out. But don't panic and be messing with the dial because it goes up to 300, or below your set temp. Just leave it where it is. That's not going to be a big problem over the course of the smoke. Pork butt is a great first smoke to break it in. It's a long smoke, and pretty easy and forgiving as far as finished meat temperature range.
Don't worry about your wood catching fire during seasoning. It will be fine. If you find your wood appears to be combusting, you can take measures such as creating a "foil boat", or purchasing good quality wood (double filets) that has proper moisture content from someone like smokinlicious.com. I wouldn't worry about it too much right off the bat. Just get some meat in there and see how it tastes.
It's rare that smokes come out bad, no matter what you do the first time. Once you do a few smokes, you can fine tune things to your taste. Things like set temperatures, desired meat temperatures, quality of wood, species of wood, wood amount, seasonings, rubs, marinades, brines.