Figuring out calories / macros

If you put your characteristics into your MFP profile, MFP will give you a starting calorie estimate and nutritional goals. Try to come close to the calorie goal, like +/- 50 calories on average over a few days. If the key goal is weight loss, I'd suggest you focus on calories and satiation first, then nutrition after those things are pretty dialed in. (Calories directly control weight loss. Nutrition is important for health, but its effects on weight loss are indirect at most.)

If you have 100 pounds to lose, it's probably fine to shoot for 1.5-2 pounds a week for a while, though IMO it's smart to slow the rate as one gets lighter. It's always OK to lose slower, though, if that makes the routine easier to stick with long enough to lose a meaningful total amount of weight. (A moderate/slow loss rate can get a person to goal weight in less calendar time than a theoretically fast loss rate that causes deprivation-triggered bouts of over-eating, breaks in the action, or even giving up altogether.)

After following the MFP calorie goal for 4-6 weeks consistently, you can fine-tune your personal loss rate by looking at your average weight loss per week over that whole time, and the number of calories you logged. To calculate an adjustment, assume that 500 calories per day is a pound a week. (Use arithmetic for fractional pounds.) If you're of an age/stage to have menstrual cycles, compare your body weights at the same relative point in at least 2 different cycles to estimate average weekly weight loss, because hormonal water weight fluctuations can be surprisingly extreme for some women.

For nutrition, the MFP default goals are a reasonable starting point for most people, too, as long as they don't try to lose weight super fast. (There's no way to get adequate nutrition on too-few calories.) It's OK to adjust the goals (within reason) as you learn what keeps you full and energetic, because that varies somewhat from one person to the next. Most people would treat protein and fats goals as minimums, while carbs are more flexible. (That's because protein and fats are "essential nutrients" in the sense that our bodies can't manufacture them out of any other intake, so we have to eat some.) If you prefer low carb, it's fine to reduce your carb percent goal accordingly, and allocate those calories to protein or fats. (I don't do low carb, personally - but that's a personal preference thing.)

The above advice is based on my experience losing from class 1 obese to a healthy weight at age 59-60, and 7+ years of maintaining a healthy weight since (after around 30 previous years of overweight/obesity).

I'm cheering for you to succeed long term, because IME the results are very much worth the effort. Best wishes!