FYI, the story you wrote is not the story you want to tell @ your next interview. Too long, for starters. It also sounds like its not your fault, but rather the LCA's fault for not hearing the whole conversation, or the seat support guys fault for leaving certain items on. That may very well be the case, but you can't say that in an interview. I've quoted the parts you need to take out.
Here's your new story:

I mistakenly allowed certain de-icing items to be left on when they were not supposed to be on during an abnormal checklist. I misinterpreted a conditional statement in the checklist as "if you are using it" vs. "if it is required by conditions". I learned that checklist discipline is important. The checklist is there to enhance safety, and it is important for me to use every resource at my disposal in a situation to bring the highest level of safety to my flying. I haven't had any training issues since. . . . Or something like that.

It's my fault, this is what I learned from it, and I'm a better pilot for it. I am safe, I have good CRM, and I don't have a record of training failures. Mention the failure, take ownership of it, and then spend the majority of your answer on why you're a better pilot b/c of it. The training failure doesn't define you, it enhances your skill set.

Any pilot who's been in this industry for awhile either has a checking failure or deserved one, but was lucky enough to not get one through a benevolent evaluator or one who just didn't catch the mistake. It's not a big deal to make a mistake. It's how you handle the mistake and what you learn from it that is the key, especially in an interview.