A PR application is not a job interview. Either you qualify or you don't. If you had qualified under CEC for example, it doesn't matter if you lose your job, quit even go back home, your PR still gets processed.
However, if you applied with a full time permanent job offer and the employer who gave you your job offer then lays you off permanently, you no longer have a job offer and this could jeopardize your PR application if immigration finds out.
There is no such thing as "taking over" a closed WP. You would need a new LMO and a new WP.
I doubt you will get EI either with a closed WP. You can try it but they will most likely tell you that it's not fair against Canadian applicants that they have to take any job that comes along while you collect benefits because the employers looking for people are not willing or able to get a new LMO for you.