I think he lied about who wet the bed in an attempt to distance Kim from the master bedroom.  He'd tucked her in, he didn't know about the four blood types and when caught, like some children, he just keeps insisting on his lie.  He may even believe it by now. 

Why the lie about CPR?  He's a doctor.  To not have tried it would reflect badly on this (in his mind, imho) fact, so he said he did what a 'normal' doctor would do in the situation - but he failed to match the scenario to his words.

Remember, half of what JRM says is to impress, the other half to cover his posterior - if you keep that in mind, most of what he says makes sense (it's still not true, but it makes more sense)!