Your run looks predator proof and if it is I'd remove that whole wall.
I'd not worry about drafts if I were you. That doesn't really affect us down here in the south were it never gets too cold to have to worry about cold air blowing on them.
Oh boy....
Based on this picture you are going to have a serious heat issue come next month.
Post in thread 'How often to offer grit to 8 week hens?' https://www.backyardchickens.com/threads/how-often-to-offer-grit-to-8-week-hens.1576985/post-26790874
I'd cut that whole wall out/off if I were...
You didn't ask but I think you have a few other things that you might want to consider changing soon.
The roost bars are too thin and too close to the walls.
You might want to consider raising that bottom one up just above the circles cut out on the left wall and changing it to a 2x4.
That top...