Weight loss and walking after my injury/surgery: Your opinion?

So, two years ago I weighed 180 labs at 61". I have sciatica and an IT band injury, low impact cardio became my best friend not walking. 30min a day on the arc changed my life.

Your probably better off switching over to something like swimming, I know it's a bit more difficult to work that into a daily routine... however I'm sure your knee will thank you.

To be motivated to do the wrong thing is a bad plan. First. Weight gain boils down to taking in more calories than you burn. A possible cause is diabetes and not lack of exercise. A second cause could be hypothyroidism which slows metabolism. A third possibility is you did not clear your plan with a doctor or physical therapist which is why you're asking us. A fourth possibility is as you age most people's metabolism slows down. Your weight gain, weight loss, injury, weight gain. Is a typical jock kind of pattern. So, it isn't exactly unusual for anyone to do this. So don't let yourself get angry or embarrassed at me for what I am telling you. Remember that you asked.

Before you do anything involving that knee you need to be motivated to see three people who are professionals, not Curly, Moe, and Larry, or Shemp. You might be playing the part of Shemp even, treating yourself with a public opinion poll.
1. You need medical clearance from your surgeon, who will...
2. Send you to the Physical Therapist for an examination and evaluation. You did that but maybe it seemed useless to continue because you were fine. So, maybe you just quit without going back. Now, maybe you're afraid to go back, and want us to support you in that decision. Nobody should do that on the entire Internet, so withdraw the question.
3. See either a nutritionist or a dietician who can explain how to adjust your caloric intake to fit with your ability to exercise. Keep a food diary and write down every tiny morsel of food each day. If it a measured amount, include the measurements. If it is a cheeseburger from McDonald's or any other fast food place. They can supply you with a list of their products and the amount of calories in each item. This will help in figuring normal, and how to taper it down to more helpful.
It is natural for anyone concentrating in a particular area of physical training, and seeing success to think its the only way. It never is. Low impact aerobics, pool therapy, passive exercise or no resistance exercise can keep your weight in check, create a positive feeling to motivate your continuing, protects your knee, and it can include the family at the pool or beach. Also, don't start any exercise without a medical clearance. That will help keep you alive and lower your risk of permanent injury. Which is what we agree, you don't want. Also, destress yourself. This situation is workable, triple heart bypass, much more complicated.
I am not a doctor, these are my opinions only. Seek the advice of a competent medical provider for treatment.
I practiced medicine for 20 years in service. Navy, Marines, and Coast Guard. Life experience would at least make me a physicians assistant, but I am not one. I only stepped into this conversation to educate you enough to stop what you're doing.
Jerome Newland HS1 /USCG /Ret