Many Attorneys will travel directly to her to help her with her Will. While the online forms can be legally correct, it is my experience they are not drafted corrected nor signed correctly leading to more problems in the future. My advice would be to find an Attorney who makes home visits.
The primary proceeding will need to take place in Florida with an ancillary administation in NY. If the only asset in Florida was a home and it was homestead property, you may be able to qualify for a Summary Administration in FL. It is likely however that because of property in both States, you will want to proceed with a Formal Administration in FL to allow for the appointment of a Personal Representative to handle all of the Estate affairs.
Under Florida law he would have been required to file a copy of the Will with the County Clerk within ten days. It is likely the property was transferred without a Will and he had some type of ownership interest in it. You can search at the County Clerk website for the deeds and review how the actual transfer took place. My recommendation would be that you contact an Attorney who specializes in Probate Litigation.
If you Will was valid in Maryland it would be valid in Florida. However, every states laws are very different and I would suggest that you consult with an Attorney in FL related to updating your prior Will.
Sending the Waiver prior to the funds is common practice, however I would inquire about a informal accounting, the amount of your share and when it will be sent. You typically would recieve this information along with the Waiver. As a beneficiary you are entitled to request an actual formal accounting and not at all required to sign such Waiver.
A Will does not need to be notarized to be valid. A Self Proving Affidavit attached to the Will would allow the Will to be admitted without finding the witnesses to the Will. However you can admit a Will without the Self Proving Affidavit, it just requires some additional steps. If your father does not have capacity at this time, you will not be able to do anything to correct or change the document.
By publishing to creditors it allows you to limit the time with which they can file a claim. If you do not publish, creditors will have 2 years to file a claim against the Estate leaving the Estate liable for a longer period.
In order to obtain the homestead exemption you would need to be a permanent resident of Florida. Your father's homestead exemption should not affect your ability to homestead the property once it is in your possession and you comply with Florida Statutes.