I think - and I'm not an expert - if Kai is not screaming after a feed and going down and sleeping well or being content, and if he has plenty of et and dirty nappies, you should be ok.
Also, I don't know about the most you can express in one go, I was told never to exceed 15 minutes per breast as it could make me sore.
I agree about the breastfeed, Naomi took two which wore me out and left me not knowing what she had taken and when she would wake. If he is getting the milk and it's easier for you then go for it. Just bear in mind that it will get very restrictive unless you can express ahead, which is what I try to do, so I can have some freedom to go out to the shops etc.
Sue