Father who filed jointly with mom on previous year and is now my dependent.

I'm claiming my dad as a dependent, but the previous year he was on my mom's joint return.

I have paid well over 50% of the support for my dad and he only has SS income and less than $200 of interest.

They had a refund for that joint filing year which they applied to the next year.  My mom also made estimated payments for the year that I'm claiming my dad as a dependent.  The year I am claiming my dad as a dependent, my mom will file as a single taxpayer.  They are still married.  Since their previous year refund is half my dad's should I claim dad's half of the refund on the return that I am filing with him as a dependent or should my mom claim all of the refund plus all of the estimated payments?   Also my parents had a joint Edward Jones account (although it is reported to IRS to my mom's SS#) 

I assume I should report all of my dad's income on my return if I am claiming him.

What do I do about the refund for the previous year that my parents had applied to the year that he becomes my dependent?

Also should I claim half of the Edward Jones income or let my mom claim all of it on her return?