1) I can not see this as a display of intelligence, really I think that what is more on display is that Malcolm and Reese both fail miserably at relating to females, and Dewey still has his cuteness on his side. So, Dewey wins by being cute.
2) Again, this is not a battle of intelligence. Dewey is clearly the more rational of the two, and Malcolm has issues that allow him to have a low price on his self esteem - but that is a common idea with Malcolm.
3) More of Malcolm's failing with relating to women Now, how "smart" is it really to drug someone? With ready-to-apply drugged sauces? No, not a display of smarts.
4) This is a better example - but seriously, short of working together (which would have been a simple solution: "Lets drop Dewey off first"), how could they have won? It also highlights Malcolm's obsession and desire to do destruction
5) not really a good example of one-upping, as Malcolm was so zoned out to begin with Its more an example of great strength - moving both mattresses and Malcolm whilst keeping Malcolm asleep...so, should we assume that Dewey is stronger than Reese from this episode? Has it been 'left up to the viewer to work it out"?
Anyway, I am still on season three in my rewatch, where it is still very obvious that Dewey is not a competitor for Malcolm's smarts. Although, some of your examples, Convention and Dewey's Dog, do come from that era!
Remember that in Dewey's Dog, not only was it not a smart thing to bring home the stray dog, but he 'beat' his brothers simply by force/strength, and Reese 'outsmarted' him in regards to the roast! Finally, they were able to get rid of the dog, and won in the end - does this mean that Reese is also smarter than Dewey?
There was also a cold opener in S3 where Reese and malcolm were catching a ball, with Dewey trying to join in. When it went in the gutter, they convinced him to go in, promising that they would let him join. But they didn't. And Malcolm mentions that they had done this over 50 times. Clearly, this is not a point in favour of the Dewey-is-super-smart camp