You may take whatever action on behalf of the client as is impliedly authorized to carry out the representation, such as filing necessary pleadings.  ER 1.2(a).  If you plan, however, to disclose sensitive or private information about the client in the pleading or motion, the best practice is to discuss your plan in advance with the client.

No.  The client retains the ultimate decision whether to settle a matter.  In a criminal case, the lawyer must abide by the client’s decision “as to a plea to be entered, whether to waive jury trial and whether the client will testify.”  ER 1.2(a).

Clients normally defer to their lawyer regarding technical, legal, and tactical matters. Here, if you are unable to reach a mutually acceptable resolution, you need to decide if you can still provide competent and diligent representation to the client if you abide by his call on the expert. If you feel strongly on this “means” disagreement, you may need to terminate/withdraw. See ER 1.16(b)(4).

A lawyer’s representation of a client “does not constitute an endorsement of the client’s political, economic, social or moral views or activities.” ER 1.2(b). (If your political views might materially limit your willingness or ability to provide the client with competent and diligent representation in pursuing the client’s objectives, you should evaluate whether you have conflict of interest. See ER 1.7.)

Yes.  ER 1.2(c) allows you to limit the scope of the representation provided the limitation is reasonable under the circumstances and the client gives informed consent. Make sure to consult the appropriate set of procedural rules for how to do this in litigation. Also make sure that the limitation is clearly spelled out in your retention agreement, which you should ask the client to review and sign.

If it is reasonable to limit the scope of the representation in this way and client gives informed consent, the ethical rules do not prohibit ghostwriting. However, some tribunals may require disclosure of an attorney’s role in assisting pro se clients, and so caution is advised. See Ariz. Ethics Ops. 91-03, 05-06, and 06-03.

ER 1.2(d) allows a lawyer to discuss the legal consequences of any proposed course of conduct and “to counsel or assist the client in making a good faith effort to determine the validity, scope, meaning or application of the law.” If, however, “a lawyer comes to know or reasonably should know that a client expects assistance” with criminal conduct, “the lawyer must consult with the client regarding the limitations on the lawyer’s conduct.” ER 1.2 cmt. 14.