Happy to reply your queries by the same order you have asked :-
1. I have received my WP extension so just hang in there, it takes a bit of a time, i applied end of october and received it in mid january.
2. I believe people in this forum has mentioned ways (as in what digits to press) to reach to an agent, but it won't help much. I reached out to them 3 times and all they could say is wait and see.
3. If the processing is not done on time, you are still eligible to work. You can find the guideline for implied status on IRCC website and if a decision is not made on your file by the date they mentioned you are eligible to work,. The date they mention is not a deadline, it is just an expected timeline.
4. You can call an agent and tell them tp update, they will update it and all the documents will be send to your new address, i did the same thing,
5. I don't have much knowledge, changing your jobs on implied status is hard, but can still keep applying to new jobs, you can discuss that with your new potential employer during the interview stage and see how it goes.
6. Until you get your new Work permit, your SIN number will not be extended
7. Yes you can work on expired SIN, i got my new one this week (mine expired in Dec), you are expected to update it asap but in no ways it is against the law.