First time smoking Chicken Breasts

I like my poultry to smoke between 280* and 325* (or more). I like the finished product better that way.

Everything else sounds like you did good!

That is a nice looking ECB with those mods.

As for the chicken, breasts are hard to keep moist as there is little to no fat. You could try bone in skin on breasts and see if you like that better. I personally think that leg quarters on the smoker are the best part of the chicken.

I like to filet breasts like that open and stuff them with cream cheese and jalapeno or asparagus or whatever sounds good, then wrap in bacon. I have also made chicken courdon bleu with ham and swiss and blue cheese and they were fabulous.

My wife is all about boneless skinless breasts for the low fat, but on the smoker I use skin on, and rub herbed butter under the skin, I pull them at 162* then put them on a hot grill to crisp the skin(she still pulls it off). Not quite as healthy, but they sure are good!

Tish, do a search on brines here, or come up with your own.  Brining is a nearly 100% surefire way to keep the breasts moist.  My grilled / smoked chicken breasts are a family favorite.  I cook them on my UDS at about 325 degrees, for about 20 minutes per side, until the thickest part reaches 160, then they rest for 10 to 15 minutes, slice them and enjoy.  Before I flip them at the 20 minute mark, I'll baste them with olive oil, flip them then baste the other side.  Gives a great golden brown color finish to the meat.  My brine is a bit salty for most so you might adjust as necessary, I use 2 quarts of water, 1/2 cup kosher salt, 1/4 cup white sugar, then 1 packet of whatever dry seasoning mix or marinade hits me at the grocery store that day.  For use with Italian dishes, I buy the Zesty Herb marinade packet.  For a bit more spice, I'll go with the A-1 Chipotle marinade packet.  Brine for 3 to 4 hours, then rinse off and get on the smoker..