No, the wood is too soft. You need to use a hard wood such as oak.
Maybe. The rule of thumb is 30" for 3/4" plywood, and 36" for 3/4" solid pine. This is solid pine, but is only a little over 5/8" thick. So - it would sag more than a true 3/4" thick piece, but perhaps not too badly. If you could screw a 1x2 rib lengthwise underneath it, or attach it to the front as a "lip", it would stiffen it tremendously.
Cross-cut yes, rip, no. That's their policy. But, the panel saws they typically use rotate 90°, so the saw is physically able to perform sheet rips, if you can only convince the employee to do it! Brownies are traditionally a good "thank-you" for contractors.