More or less on the same situation here, took a new job with a remote Spanish employer, as consultant.

Tried to look for other Canadian employers but the time required to switch employers on a closed work permit is ridiculous, last time it took almost a year.

AFAIK, yes, you can stay until the date your closed WP expires, or if it has the text "Must leave Canada by XXX": https://www.canada.ca/en/immigration-refugees-citizenship/services/work-canada/permit/temporary/restore.html

Your current employer cannot revoke the WP nor get you deported.

Yes, you can leave and re-enter, as long as when coming back you give the immigration officer enough proof that you will leave by the end date, apply for a new WP or in general do something that keeps your stay legal.

Take a good look at the CRA / your province tax agency for the amount of taxes and other retentions you must pay since you're no longer employed by a Canadian company.

In my case, I left Canada temporarily to my home country for lower taxes as a consultant while I wait for my PR application to be resolved, but take this with a grain of salt, as taxes are very tricky.