Under the current laws, if you change jobs after I-140 approval you keep your priority date, but you lose your right to H-1 extensions beyond what is given if your old employer revokes/withdraws the I-140.
Now answering your questions
Answer 1.No, you will get an H-1B extension for the time remaining and you can actually claim one year extra if your PERM was filed more than a year ago. But you will get only three years if the I-140 is approved. Not if it is pending.
Answer 2. I don't recommend it. I think you should get your I-140 premiums, get it approved and then leave if you want to.
Answer 3. I don't think that is a major issue, but do talk to your lawyers. Hence it makes sense in my view not to change until the I-140 is approved.
Note: This is a verbatim transcript of the referenced audio/video media delivered as oral communication, and, therefore, may not conform to written grammatical or syntactical form.
Hi Mr Khanna ,
I am highly thankful to you to take my father's case of B-2 visa extension which is just got approved. I appreciate your business. You team is excellent and very helpful. I got all my queries answered timely and a very good manner. Now I will be in touch with you for further extensions and any other case. Also, I will suggest your name for my near and dear.
Thanks again Regards Deepak Kumar Gupta