17 year old Male here. 184cm in height. approx.100kg in bodyweight. Have been weightlifting for 3 years. Have been in a bulk for the past 7 months or so and am now beginning to cut. I am currently training 6 times a week. 3x strength training sessions a week and 3x running sessions a week, although the running sessions are only a 1.5 mile loop which is about 15 minutes of running and the strength training sessions tend to last about 60/70mins According to MyFitnessPal I should be eating 2100cal daily down from 3.5k cal a day which is said to be my maintenance level.

1. Is my caloric deficit too high and too aggressive?
2. Should I cut back/ increase my cardio or strength training?
3. Are calorie calculators and MyFitnessPal at all accurate? I gauge my body fat % to be around 18-20% ( slight definition in abs and slight vascularity in forearms shown ). I will be cutting for about 8-10 weeks but can go further if needed.

Thanks.

P.S; I have never cut before, so I don’t want to screw up and lose lean muscle mass or go into an overly aggressive caloric deficit.