Just starting

Congratulations on losing 2 pounds in two days! You'll find keeping track of what you eat really helps you stick to an eating plan but I would voice a word of caution regarding your goal of four pounds a week for the next six weeks. Inevitably the rate of weight loss drops off the longer you are on a diet so you may have the odd week when you don't lose any weight at all. that doesn't mean that your body isn't changing, though - it's definitely worth perservering.

Four pounds a week is really not a good plan . . . it's much too extreme for your current size, and I fear that even trying for that will take you into your surgery in a state of depleted health. I can't speak for you, but at age 66 myself (and a reasonably fit/healthy 66 at that), my resilience is not what it was at age 20, so the consequences of any physical stress tend to hit harder now.

In order to lose 4 pounds a week, you'd need to eat 2000 calories fewer on average daily than the number of calories you burn. An average height (5'6") woman of age 61 at 200 pounds would be expected to burn maybe 2300-2400 calories daily with a physical job and/or 5 days a week of fairly intense exercise. The implication is that to lose 4 pounds a week, that woman has to keep up that activity level, while eating just 300-400 calories daily. Less active than that, there are even fewer calories on the table to eat.

You're proposing to do something on that scale between now and mid-May, so 5-6 weeks? I'm sorry, but that's seriously not a good idea.

If you prioritize your health, please don't try. I'm surprised that your doctor's even willing to do a lipo & tummy tuck if you're still substantially overweight. Most folks here who've had those procedures have said their doctor wanted them to reach a stable weight and stay there for months, maybe a year or more, before having the surgery.

I'm sorry to be throwing cold water on your goals, maybe that's wrong of me, but I'm concerned that you're jeopardizing your health.