counting multiple health conditions overlapping

I cannot find the info I need in the forum so I will ask for help. I am full time carer for my wife and she has been invited to apply for PIP as her DLA is to end, My wife has severe scoliosis causing her upper body to angle sideways so her ribcage almost touches her hipbone causing pain and breathing problems due to chest compression. This also leads to leg pain due to nerve compression. She has been a type 1 diabetic for almost 30 years and has some loss of hypo awareness plus neuropathy in her feet. She has arthritis in her shoulders and hands with gnarled fingers and swollen finger joints for which she has injections every few months.
The part I am trying to understand for her claim is not being able to carry out the activities for the descriptors more than 50 % of the time when several health conditions are a factor. For example, she is pain from her scoliosis 100% of the time but to varying degrees so she may be able to perform some cooking, for the sake of argument, 4/7 days meaning she doesn't qualify for pip. However, her arthritis may be too painful for her to cook 4/7 days but these days may or may not not all coincide when her back pain does. Does this mean she may be incapable of cooking all 7 days per week if you add both conditions together, in other words, incapable of carrying out the activity MORE than 50 % of the time?
And how do I account for her diabetes hypos? These are random and can strike at any time meaning I have to supervise / help her for cooking, bathing, travelling etc.and keep watch over her during sleep IN CASE a hypo strikes and she in is danger. (there has been countless occasions when she has slipped fast into a hypo and I have had to revive her or call paramedics in)
I have downloaded the guide and studied it but I am still floundering a bit. Can anyone offer advice how to approach completing the form please?