Wow 12lbs is amazing, well done. Now you can't honestly expect to lose 12lbs a week as that isn't realistic unless someone weighed about 50st to begin with.
I've done a VLCD many times so I'm well versed. Taking 2 packs a day will mean you're only getting two thirds of your daily nutrition as each pack provides one third of all the RDA of vitamins and minerals.
Everyone has a big loss on a VLCD at the beginning as it's mainly water weight and then it levels out to between 2-4lbs a week So please don't be disheartened, if you're taking your 3 packs a day and drinking plenty of water (2-4 liters a day) then you're doing everything right.
Also don't worry about ketone strips, they're not necessary. A light to dark pink is optimal for ketosis, your fella might be burning at a higher rate as men lose weight quicker than women. Sad but true.
Anyway you're both doing excellent so keep up the good work!