Looks pretty good for your first time.
Did you use a binder like Mustard or Oil before applying your rub? If not, next time I would recommend putting a layer of plain old yellow mustard on the ribs before applying your rub. You will get a nice bark during the smoking process and you will not taste the mustard at all.
What rack did you have the ribs on? You'll want them to be up as high as you can do without touching the top of the smoker as the temps are more stable toward the top of the smoker.
Regarding temp swings, a 20 degree temp swing is at or below normal, so nothing you're going to be able to do about that (and that is OK) unless you purchase an Auber element control unit. There is a whole section for the Auber on the main page.
Personally, I don't mind the temp swings and my temp swings are typically closer to 30-40 degrees. In the end I don't think it affects the taste at all. But if you want to remove the swings the Auber will do it for you. The biggest benefit of the Auber though is that it lets you program your smoke. So, if you like to ramp up your temp at the beginning of the smoke to help prevent the notorious "Belch", you can program that as well as set a resting period at the end of the smoke once it hits the meat temp that you are looking for.
But for ribs, next time I would try smoking at 235 and checking them after 4.5 hours.
I think you're good on the wood. Typically you'll want to use between 2-3 ounces of wood depending on how much smoke you like. I like a fair amount of smoke, so I typically run closer to 3 than two, but that's just me.