good to see your determined to keep on trying. personally, i'd shitcan the foil all together, it's too hard to get smooth enough to prevent hot spots for one thing and it's just not very reflective for another, go buy a can of flat white spray paint, try to find the kind made for painting plastic, maybe the kind made for model cars.
also, you'd probably be better off with a passive intake rather than trying to put in an intake fan, if it's not done just right, they compete with each other and create LESS air movement.
here are some pics of a Rubbermaid box made by 'smokedoja' that he posted on another forum, hopefully, he won't mind my sharing them here with you. i'm not gonna post ALL the pics, there are several, so if you need more, just ask.
anyway, i hope this helps

bozo,
peace, love, dope