I'm not familiar with the VP system, I have a mercruiser. That said, the diagram you posted looks very close. I found the elbows on mine were rusted to the point that the exhaust was not being cooled.
I think your over engineering it a bit but it's your boat. fillet is not necessary IMO. and even using yellow pine lumber will last you many years, The PT lumber these days ain't what it used to be..
It doesn't look life threatening, my kitchen faucet drips more. Another option is the seal for the raw water tube, they can take a beating when changing the hose..
