Question #1 – The cylindricity will allow a total size variation of +/- .0007 or .0014 local size and the size variation allowed by AVG is .0005 on diameter. The specification seems ok to me however I am not on board with the functional requirement you seem to have specified – convince me this is what you actually need. BTW, functionally why not invoke the independency (Circle I) on the FOS? Seems this specification may be more applicable for the functional requirements to me.
Question #2 – Looks good to me.
Question #3 – Yes, datum C is a derived axis from the cylinder and will locate the center of the keyway FOS center-ish.
Question #4 – Yes, the Datum axis A-B will center the splines. I assume that both datum’s A and B are bearing locating surfaces in the application assembly? It’s correct to specify which feature of the spline the position tolerance applies to however I don’t think the parentheses are required.
Question #5 – Looks good to me however you might consider some reference information for the manufacturing folks. If this part is manufactured on a vertical mill, not CNC extra data is helpful. Therefore if you extend the centerline of the angled hole to the intersection of the datum axis D and reference dimension it manufacturing might find that data useful – just ask a see what they say. Also, intersecting holes are going to be rough and burr prone - a note specifying what is acceptable should be on the engineering drawing. Also, the horizontal drilled hole you intersect with needs to have a drill point.
These are not “Rookie“ questions nor applications, just saying.