You can only file a default if you have proof of service, or if they accepted service in writing. I would call the clerk and make sure you have all the final paperwork completed or call an attorney for a free consultation to better ascertain your situation.
This can be answered in a lot of different ways, and without seeing the exact language on your Decree this is difficult. From a technical standpoint her portion of your retirement does not change in that her amount is figured and can grow or decrease depending on the type of retirement. This also can be based on the QDRO language. I would fight it if you are unsure or have a consult with an attorney who can review the specific paperwork.
One thing I would do is call your local bar association for lawyers in your state and see what pro bono services they have. In most states attorneys are required to do a certain amount of free work. Good luck.
You have to be careful with this. The reason is if the property is considered marital she may be entitled to half the value and not the sale amount. The court may also think you are trying to defraud her.
You may be able to contact Utah Legal Services for some free legal help. They may be able to help and give you the case law you are looking for. I would also cite the rule that you have found on service.
If you have gone to trial, or are going to trial you need to make sure it is an issue certified for the judge to decide. If you have reached a stipulation you need to include it in the Decree with notice to your ex-spouse.
Yes, you need to get this corrected. The length of a marriage effects other items such as alimony. You can send in a corrected Decree in order to fix the problem with a simple motion to correct the order. Good luck.