Sum up using 64 bit floats

A 32 bit int would probably work for three or maybe four years. More
than that risks overflow.
Calculate league averaged regressed to desired PA
Add league average to each player's projection
Simplify iterating over matrix rows

The totals seem to be slightly different, so not sure how much rounding
is happening.
Save the shape of the season matrix for later
Start projecting PAs
Reshape into a column vector and then add