I'll attempt to answer your questions in order.
1. File a state complaint. That's your only leverage at this point. Your complaint/compliance issue would be that the school district is not complying with the requirement to have parent participation during the IEP process.
2. Paper train for your state complaint. Additional compliance issue: failure to provide PWN and failure to response to request.
3. You're going to have to force the consequences by filing a state complaint.
4. I find it hard that an initial IEP (which this is, correct?) does not have to be signed by the parent. Usually the start of providing special education services requires consent by signing the initial IEP. After the initial IEP, continuation of services in subsequent IEP documents can usually be done without parent consent (but this is state specific). If you are getting no response to your requests to be involved, their only motivation at this point will be a state investigation which will occur after you file a state complaint.
5. Again, your only recourse at this point is a state complaint. In addition to the above, also list "failure to comply with 60 day timeline." The state is going to have to be the entity that provides the consequences.
Usually state complaints are not hard to file and do not necessitate an advocate or attorney. The state provides you with a form. If you have questions about it, you can call the special education department (compliance division?) of your state department of education. They should be willing to assist you in completing the form. They might also have a list of agencies (free) to which they can refer you.