Hi Sherbs - I am sorry to read of the issues you are facing. Applying to register a property for the first time can be confusing so if you are not going to use a conveyancer then I would recommend separating the process and application into separate parts
The two key first steps are the probate, which you now have, and the actual deeds that confirm his legal ownership. You will need the latter to be able to prove that he owned the land/property as appropriate and they will also influence the type of application and supporting evidence you then need to submit.
Once you have those you can then complete
forms FR1 (application form) and
DL (list of deeds/documents you are submitting)
Form DL should simply list the deeds/documents in chronological order, so eldest first and most recent last - the most recent would be an
Assent (form AS1) from yourself as the executor to yourself as the beneficiary and new legal owner.
So FR1 and DL first and then Form AS1 second re the key forms you need to complete
Form FR1 includes side notes to help explain the information to include - panel 4 would be Absolute Freehold as you have the original deeds and documents
You will need to have your identity verified and if you do not wish to use a conveyancer for that then form ID3/others as listed in PG 67 can be used -
Evidence of identity (PG67) - GOV.UK (www.gov.uk)
There is a lot of ground to cover but much of it is 'paperwork' so by doing one form at a time can help but of course what might be simple for one person may prove complex for another - if you have any friends/family to work through them that may be an option also.
There's a limited to the advice we can provide beyond what you have already obtained and the forms/linked notes and more but hopefully you can do as suggested and submit an appropriate application once you have the deeds/documents to hand