So, she thinks I'm cheating on her (I'm not)

[Fake Boris]

Maybe she's pissed at him for being sick, but realizes that this isn't an acceptable reason to be pissed at him, so she's (sub)consciously fabricating more acceptable reasons to be pissed at him. I know from second hand experience that people get angry at other people for their being sick, then they feel guilty for these feelings, and the combination of anger and guilt can get pretty bizarre.

This.

[dannubis]

Do as Dinner said. If it doesn't work, draw your conculsions but fear for being alone is not a reason to spend the rest of your life - as it is - miserable.

[OneFootInTheGrave]

If she is in denial about your illness, for sure this is the cause of such weird behaviour. Ultimately you will need to sit down and talk, disucss what would be good for both of you and the kids given the situation and try to make best of it.

Some sort of "facing the truth" discussion (which is unfortunately one of those few cases that are worse than if you were cheating), should be on the table.

[kentonio]

For years I've let her vent first, say all kinds of things, and then after she calmed down, told that I will not tolerate this kind of behaviour.

Perhaps you're long overdue a bit of a blow up of your own. Over time people can come to mistake reasonableness for weakness.