I burn 1000 calories per day at work. Okay to do prolonged fasting alongside it?

I’m very experienced with fasting, mostly 36 - 72 hour fasts. I used to be completely inactive when fasting (and in general too) but on a break from university so working at a grocery store for the time being. My Apple watch tells me I supposedly burn 1000 calories per day I work and walk around 13 miles. I work four days a week so that’s about 4000 calories per week burnt and my BMR is 1700 calories. So if I fast for the 4 days (in a row) I work per week that’s 4(1700+ 1000) calories burnt which is 10,800 calories per week. Using 3,500 calories needed to burn to lose a lb that equates to roughly 3.08lb of fat / 1.4kg burnt per week if I fast 4 days in a row alongside the activity I do at work (which I know is not an exact science but a good estimate to star with at least I feel). Need to lose at least 10kg so going to do it for 10 weeks plus. Is it fine to do prolonged fasting alongside this sort of activity since I’ve never gone about fasting like this before? I don’t feel particularly tired doing it this way, especially with a ketogenic diet with roughly 20g of carbs, but just wanted to get a second opinion.