You can't trust some dealers!
You may have to drain and refill....
I use 2 cups of calcium chloride in 400 gallons of water, don't know if that's 1/2 pound or not.
Get onto either chlorine or bromine, there are proponents of both here and either way you can be helped. AND get a Taylor test kit! You need to know you water chemistry ... don't leave it up to a dealer. You need to measure PH, alkalinity, calcium and sanitizer. Most kits will have a stabilizer test ... change the water every 3 or 4 months and don't worry about this.
Bromine and chlorine are the two sanitizers that are used mostly and we all have great success with both systems. Non chlorine shock is useful for your weekly or biweekly shock.
As far as temp ... hopefully some Jacuzzi people will come along and chime in.