I don't have good advice about joining an addiction group, since I haven't been to one before, so my advice is not the best, but I hope it helps
I started to notice that I have a binging problem this year. My first binging experience started 9 years ago, and it stopped just as fast as it started. The problem only lasted a few weeks. However, since the beginning of this year, I started binging again. For me, I think I do it because of my self esteem issues, feeling sad, and also when I restrict (when dieting) as KRAMPUS has mentioned as well.
Since you have lost so much weight, your skin now is a bit loose, and makes you feel ashamed and lowers your self esteem. You said you ate very well yesterday, but then got depressed. What made you feel depressed? Is it your skin on your arms? Being stuck in the 160's? Something at work?
That's when you started to eat the snacks in your work desk drawer. Are they healthy snacks? If not can you switch them to healthier snacks that you won't want to binge on?
After eating these snacks, you realized that you had one too many, but then you thought "Why not go all out and get more food at McDonald's?"--is this a familiar voice you heard in the past when you were overweight? Maybe you've done this before when you were overweight, and this was your usual way of dealing with the depression/stress/self-esteem issues. Everything would be going well...then a slip-up happens...then you realize you messed up...and then instead of controlling the damage, you just let yourself sink into it. This is a habit that you haven't completely freed yourself from since you've started to lose the weight 2.5 years ago. Look at me, it came back 9 years later.
You said you enjoy going to the gym every day, doing 1400 calorie burn workouts, and perhaps your consistency in working out really hard and even enjoying it may be making you feel conflicted about it (when you're not working out) since you've been "stuck" in the 160's and not seeing much result from the hard work you put in. However, you mentioned that you think the plateau may be due to the binging and perhaps an abnormal metabolism from yo-yo dieting.
In my opionion, all of this just seems like you are putting yourself in a bad cycle every week: working out hard, eating right, and binging due to stalled weight loss/feeling bad/slip-up in diet/whatever.
Now if only you could stop the binging, you could then begin to lose more weight, focus on the arms, and feel better about yourself. The good thing is that you noticed it's happening once a week. When that time comes around this week, focus on what's causing the binging, and hone in on what's going on during that time. Hormones can be the problem too, change in BC, TOM. Remember any thoughts that come to your mind and write them down quickly so you'll be able to figure it out once your mind is back to normal, and not thinking about food. If food is the only thing you're thinking of, write down the types of food you are thinking of. Maybe it's the type of food, and you're having a food craving, which can be a symptom of nutrients that you're lacking in your every day diet, thus every 5th or 6th day, you crave that nutrient (fat/sodium). So record the food you eat.
Another thing I'd like to comment on is your calorie deficit. You have 2100 cals, but burn off 1400 of them, leaving only 700 for you to survive on each day. Is that really enough for you to tend to your daily activities? Even if you laid in bed all day, a 25-35 year old woman of your height and weight needs1,494-1,444 just to live and and let your cells carry on their metabolic functions (BMR). So I would re-think your calorie requirement and exercise routine. This may help you stop the binge problem. Wouldn't that be great?! Eat less, work out less, more time to enjoy life, and less stress. No matter how much you love the gym, I'm sure you have other things you'd much rather do, and doing these things will help keep your mind occupied, and not thinking too much about food.
Anyhoo, I hope you realize you're not alone when it comes to binge eating, and I do hope that you feel better after today. You've come along so far in your weight loss journey, and despite this stall right now, you will go even further! Just know that you will!
As for your arms, you're arms will get more toned. Keep going and going. And when it's too painful...go some more! Those arms will get toned and tight. And you'll get to your goal weight. 50 pounds ago you knew you would. 100 pounds ago you did as well. And 230 pounds ago, you perhaps had an inclination. Now look at you!