I have just restarted keto after a 1 month trial before Thanksgiving.
My lap band history is that I had the surgery done about 12 years ago (Nov 2005). I lost about 60 lbs and have put about half of that back (keeping in the 200-215 lb range). I felt good at my lowest (~175). My bariatric dr. did an initial fill post surgery (winter) and I had another fill a couple of months later. I had a partial unfill 2-3 years after the 2nd fill from a nurse that was doing them in the Marysville WA area (I was about 190 lb at the time, but had a hard time keeping dense food down especially protein). She has since closed down her fill/unfill business. As I was self pay it has been difficult to find someone to do fills/unfills (I can't afford $300+ each time, probably much more now plus the price of a fluoroscope exam). I would actually like an unfill (partial or total), but am now on medicare so can't afford an unfill unless I can find someone like the nurse. My daughter who also has a band is glad she had it done (she was substantially more overweight and had many more health issues including type 2 diabetes). However, I wish that I had not had it (I only had high cholesterol, slightly high blood pressure and sleep apnea). The band has made it very difficult in social situations (eating food) and I get stressed and then it is harder to keep food down and I usually have to excuse myself and go to the restroom to BP (vomit).
As far as keto, it is not really a high fat diet unless you make it one. You should be eating good fats (olive oil, avocado, some nuts, I make keto mayo with olive oil). Since I can't eat a ton of protein, I don't feel I'm getting an overabundance of saturated fat and I try to eat leaner/cleaner cuts of meat and grass fed hamburger. I don't eat much bacon, maybe once a week I'll have a slice or two. The most important parts of keto is keeping your carbs low (20 g or less my preference or typically 20-30 when trying to lose weight) and moderate levels of protein (0.8 gram per kg of ideal body weight or you can scale down as you go if using your current weight; or see https://www.livestrong.com/article/535738-how-to-determine-protein-requirements/ to determine requirements). Too much protein converts into glucose.
Look up Jason Fung (one of the "diet doctors" on youtube). Dr. Jason Fung completed medical school at the University of Toronto and a fellowship in nephrology at the University of California. He founded the Intensive Dietary Management Program in Toronto that provides a unique treatment focus for type 2 diabetes and obesity.
He has an enlightening book called "The Obesity Code:...". He is an advocate of the keto diet and intermittent fasting.
Another good source for inspiration is youtube's "Keto Christina". She has lost over 100 lbs and is very knowledgeable. She eats a lot of Irish bacon (very lean, not much fat compared to US bacon).
P.S. I had my gallbladder removed at time of lap band due to stones and my daughter needed her gallbladder removed about 6 months post lap band surgery.
