Nic salts would give you the exact same amount of nicotine as the freebase. Their advantage is that they give a smoother hit without as harsh of a throat hit. The question is are you vaping more because you are having nicotine cravings or because you are at home and are free to vape more? A lot of people have increased their usage once they started to work from home or were no longer were working due to the pandemic. It's just a matter of access to the vape that you didn't have at work. If this is the case, you would have to change your vaping habits in order to reduce the amount you vape. For example, no vaping while working, but allow yourself vape breaks. If it is truly nicotine cravings that has you vaping more, you would want to increase the amount of nicotine you use, and since you are in the higher ranges, you might find salts more pleasant. Now I know they say that you aren't supposed to go over 12mg/ml for DL vaping, but that is not a hard and fast rule. You use what level you need to satisfy the cravings. Given that this increase started since you've been at home, though, I think that just changing your vaping habits is all you need to do.
Actually, though, 5-7 ml isn't that bad for sub-ohm vaping. I chain vape 8ml, and go through about 15ml. If you are just concerned with the amount of nicotine you are getting in a day, rather than the number of ml per day, you would want to gradually decrease your nicotine content, rather than increase it. Slowly decrease it until the point you notice you are vaping more because of cravings then stop and go back up a step. I hope that this has been helpful to get you where you want to be.