1, it might be a problem. If your future employer can make the change, it would be fine. Otherwise, you may explain it in your petition letter.
2,not sure about this one. In my opinion, four weeks prior to the filing should be fine.
3, I guess, you mean the filing fee, it should be paid with company check. You may also use money order; this way CIS does not need to wait till the check is clear to process the petition.
4, yes, it is your employer who petitions for you. what address do you think it will use?
5, if the petition is not baseless (frivolous), you can start to work after you file it. You better use certified mail with receipt to make sure CIS actually receives it.
6. The same as new one. Remember to get a new LCA, otherwise the petition will be rejected.
4.Of course, it is your employer who petitions for you.