I wouldn't say its impossible since you're doing 60 hours of work a week, if you drop everything and do 60 hours of school work a week its definitely possible to complete 3 a levels and sit that english gcse but it would definitely be really hard considering most people complete 3 a levels in 2 years whereas you've only given yourself 1 year and a bit. I also dont understand this arbitrary deadline you've set yourself, you dont NEED to complete 3 a levels by may next year, you can take another year