Employement & NHS Charges

I was move to the UK on SKILLED Worker Visa. My family (Myself, Spouse and 2 kids) with me.
As per letter we got our visa is for 5 year visa due to expire in 2027. I believe the company paid for the complete 5 years NHS charges for all 4 of us.

1) If I move to a different employment or company, do I have to pay the NHS charges for all 4 of us or only myself?
2) Will the company get back their amount they had paid for the remaining 4 years?
3) Do I have to get a job with a salary that equal or higher than my current salary?

I would highly appriciate if someone can provide clarity and what do I have to obtain complete clairty.