When you are planning to create a Lift Test, you should get rid of all the Reach and Frequency campaigns.
Unfortunately, it is not possible to pause RF campaigns on Adphorus.
From Facebook, you can pause RF campaign but its only for a half an hour. There is a limitation on RF campaigns, as you can confirm and read about in here.
Note that turning an ad set off for more than 30 minutes will require a new Reach & Frequency prediction. You'll need to accept the new prediction in order to turn the ad set back on.