my 2 cents:
1. as others have said, STAY until you have completed 7 years, your visa expiry at 7 years is perfectly normal
2. submit the application with supporting records lease, bills, etc. covering continuous 7 year period
3. you have to be ordinarily resident for 7 years, OP didn't mention his flat, while gone? OP needs need to maintain flat/bills here for contagious 7 years
4. IMHO it would be crazy to leave given the uncertainly with travel and restrictions, OP might not be able to return when you want.
5. get PR first