Which baseball resources made the most difference to your D3 player?

Something I was surprised by, that you kind of touched on, FOOD.  Our program fed our boys well on road trips and during double headers, it was ample, filling, and healthy.  I've heard of other programs serving Arby's?!? Putting and keeping good weight on during the year is hard.  It's even harder if you have to struggle to find it. Coach also coordinated meals with dining hall when boys needed a meal outside of normal hours (opened two hours early on a Saturday so team could have grab to go breakfasts, but it was full-meal made to order scrambles). The other thing that was appreciated now that we're on the other side of our first year- structured program support where upperclassmen mentor underclass academically.  The senior captain with the same major as my son helped him strategize which classes to take in-season vs out and which professors to avoid during season because they tended to be a little less flexible, in addition to the academic advisor the school assigned.

For the parents, definitely broadcast/streaming quality.  And how much or little fundraising is done.

For the players, I think longevity of coaches plays a role, as well as their number, but also, how engaged they are with whatever your son is interested in (analytics, style of training, summer ball, etc.).

How much travel, and how long it takes is important.

Some of these are location dependent. Indoor space dedicated to Baseball is a huge deal in the North and Northeast, not as much an issue in Texas, South Carolina, California etc

Big picture long term, the amount of academic scholarship money available is a difference maker.  

Beyond everything you wrote, which are indeed legit topics of consideration, the biggest factors (to me) in addition to scholarship $$$ are

1) Go where you are loved

2) Cultural and Academic Fit