Wi: the first one is wrong because only 'kasi' occurs after 'pi'. The second is right but ambiguous (but that is hard to avoid with any complex in tp). The third is fine.
Three ways to sa y "Is this all right" : ni li pona ala pona, ni li pona anu seme, ni li pona anu pona ala. The first is probably clearest, the second opens up a range of possible answers, the third does not have to be a question (though it is rather pointless if it is not).
jan li toki e ijo pi mute pona ala la jan ante li toki ni tawa ona. jan li toki pi toki sina tawa sina. tan ni la sins toki e ijo pi mute pona ala. toki utala ni li pona ala. taso mi pilin e ni: sina toki e ijo pi mute pona ala. (mute pona = the right amount)
Mato: 'en' is just fine with 'pi' (and Sonja did some runs on ambiguities and how to avoid them -- generally don't get into thing too complex) and indeed everywhere except at the head of DOs and VPs. In those places, for the divisive "and" you use repeated 'e' and 'li' respectively. So, 'en' in those slots clearly mean compound "and". But in other places, including in in modifiers (hence always with 'pi'), 'en' can mean either one and there id no way, outside context, to decide which it is. I suspect that you are right that repeating the modifier here makes it more clearly divisive, but there are no guarantees. As usual, though, not collapsing at all is better in tp than collapsing, which is part of the reason that it is so hard to do clearly.
I am eating red food and hot food, but the red food is cold and the hot food is green, vs I am eating food that is both red and hot (which is a remarkably unclear example, since it has to be a mixture, but in this case it is not different from the divisive case: moku mi li loje li seli).