My $0.02 worth.....
As a sidebar, if you are waiting specifically for an Iowa attorney to respond on this free advice forum you will be waiting a LONG time... if there ever is a response.
You need to take whatever advice you get, consider the value of it, and then either follow the advice or not... your choice.
With that out of the way... my ADVICE is:
You MUST respond to the subpoena, either by answering in FULL or by filing an objection. Since an objection is a legal filing not for the inexperienced, you might need to get an attorney to look into it. However, based on you DESIRE to not comply ("I do not want to deal with these people anymore than I have to until hearing", "they are after are identifications of possible witnesses and I don't want these people bothered", etc.) you will probably be in contempt by not providing the requested information.
Your DESIRE to not provide them information could be found to have a material impact on the opposing sides ability to prepare for trial (remember, this is supposed to be a FAIR hearing of the facts and you cannot hide these people or their statements from them). If you truly feel that your case is valid, you should have no reason to deny the other party access. In fact, they could verify that your case is solid and offer to settle without trial.
I will try to offer advice on each of your specific questions:
Q1) "Does the defendent's attorney have the right to subpoena me commanding me to produce and permit inspection of documents or objects at his office two weeks before the trial??"
A1) Yes, they have the right to subpoena any documents or records that are available to you. And unless you are able to file a specific objection to the subpoena, I suggest that you comply.
Q2) "If the defendent doesn't have the right to subpoena me (like I thought) and he has, what can I do about it?"
A2) See answer A1.
Q3) "How can I make them leave me and any prospective witnesses alone?"
A3) Normally you can't. Unless you file a valid objection with the court, both sides have equal access to information.
Q4)"Is there any way I can make the defendents attorney leave me and any prospective witnesses alone????"
A4) See A3.
Q5) "Is there anyone out there with legal knowledge in Iowa?"
A5) Apparently not.
Q6) "Do I have to respond to the subpoena in any way or not (before day of hearing) to keep from being in contempt?"
A6) See above.
Q7) "Isn't there any lawyer out there that can help me with this?"
A7) Not if you are specifically looking for Iowa help. Take what you get.
Q8) "Can I do nothing until the day of the hearing, take the information they requested then and not be in contempt of court?"
A8) Probably not. If the Subpoena requires a response prior to the court date, you could be in contempt for failing to comply.
Q9) And finally, "Without a witness do I have a prayer?"
A9) The answer is a solid Maybe. You have not provided near enough details of your claim or your proof to support it for anyone else to determine the chance of success. However, I will offer that your chance of success is far better if you have a live, expert witness available to testify on your behalf.