Hi,
I will try and answer your questions.
A) after day 64 i stopped feeding anything and if i did it was only Ghysal Greens i think.

i would check on it once in awhile and do the walks and what not but mostly i stopped looking in on my birds after day 64.
The bird you race is not directly tied to the bird you are raising in the sense that when the one in the stables' stats change your racing birds do not until you turn in another form. So there is no point of keeping going with feeding and such on the stables bird if your racing bird is current. However if you are racing to raise stats through chocobobucks i would advise not retiring it until you are done with its stats.
People say that the stats stop but what really happens is the increase you get from the plans drops substancually. Some people have reported seeing an increase post day 65 but it has always been close to day 100 so i found it bed to switch to basic care plan so as to not interfere with my chocbobuck stats increases.
High affection does increase chances of learning abilities in my opinion.
I hope this helps. Feel free to PM me with questions.
Ladymist