Hi Janet - I'm sorry to read of your loss and your Dad's health issues.
If you are to become a joint legal owner then your Dad will have to transfer the whole legal ownership to himself plus you.
You'll need
forms AP1 and TR1 (not AS1) plus both identities to be verified. You can submit a certified copy of either the death certificate or probate as evidence of Mum's death.
If you are acting as Dad's attorney then you will need to submit a certified copy of the power as well
The form A restriction will remain on the register
Whilst I understand the reason for not wanting to use a solicitor I would always recommend at least seeking legal advice as to what options exist re the legal ownership of the property and the need/desire to transfer it into joint names for example. I am not suggesting that's the wrong thing to do but we deal with the outcome of such considerations so can't advise on what's 'best' in such cases