If the squash don't develop, it's because they aren't being pollinated sufficiently. In the mid-morning, use a cotton swab to remove pollen from several male flowers. Pollinate your females by shaking off the pollen deep in the female blossom. Do that a few days in a row.
You can prune squash by just cutting off the vines to the length you want - or - instead of pruning, install a temporary fence or trellis, and the vines will grow right up it. Spaghetti squash fruits don't need to be tied or otherwise supported; they will stay attached to the vine. I guess they're not heavy enough to break off.