Perhaps get someone to pull the tail down while parked so the nose is off the ground. Then you can test the rudder anyway you please
Definately the only way to check is while moving, the first three checks as soon as the taxi starts are full left rudder, full right rudder, brakes working. When you're the one paying for the nose leg and new tyres, you certainly want to reduce the long term wear and tear/damage.
Sounds like you're having a real hard time with the 170a.