Can you go to the store at the field on non game days on weekends to purchase merchandise? Can’t find where it says Monday through Friday times, or weekends times.

Yes

Top of the Park store is open on non-game days. Just tell guard that's where you're going.

Yes, During season. Special hours off season

Not sure if it's open during non game days since the entrances are only accessible from inside the gates. I wouldn't buy gear there since the markup is steep.