For 65# at 30" I'd go at least 72" long if not 73-74"
Pin knots shouldn't be a problem. If in doubt, avoid the high arched D and go for a shape more like an inflated square (square with rounded corners) (belly corners rounded a bit more than those of the back). If the knots have black rings around them, pick at the black stuff, if it comes out loose, then excavate the knots and put little Yew plugs in or fill 'em with Yew/epoxy dust (mixed fairly dry). If they are clean and solid (no ring of black manky stuff) leave 'em alone, they will be fine.
I play better safe than sorry with knots. In the past I have had the odd pinch on the edge of a knot, but it has always been stable and never caused a failure... My Yew failures have always been from the back, not the belly.
Del