Yup, definitely gonna want a gate valve (with union) before the sump as well.
If the 1.5" drain is draining faster than your pump can pump it back up through the return pipes, you'll flood your sump.
Unions are helpful incase you need to remove the sump or pump from the system for maintenance, replacement, etc. So I would make sure there is one before and after the pump and before the sump. You don't need a gate valve before the pump, but any kind of shut off valve. Gates are more expensive and better for making small adjustments than a ball valve. But you dont want to restrict flow before the pump so a ball valve is fine there.