CreateSpace makes me spit blood from my eyes

I'm having a few issues shall we say with Create Space, Amazon's book creating website which users are able to upload their work to, then have copies printed on demand by Amazon in America/the UK. I created my book Scourge there and it took a while (also the realisation I never included page numbers), but it worked.

Comics however are a whoooooooooooooooooooooooooooooooooooooooooooooole different thing all together. I didn't know what a DPI was so I Googled it - only to have the internet laugh snarkily at me as it said "DPI doesn't exist".

IF IT DOESN'T EXIST WHY IS CREATE SPACE SHOUTING AT ME ABOUT IT I HATE YOU INTERNET AND YOUR STUPID FACE

So after a while some less snarky websites told me something about PPI (at which point I broke out in a cold sweat, felt very dizzy and blacked out) which is apparently not the type of Payment Protection Insurance I may or may not have to deal with on a goddamn daily basis, but something to do with pixels per inch or some such balls.

Anyways, long story short the internet failed to help much at all, because whilst I managed to get some of my images for the comic to the correct (apparently non-existent) DPI number (which is 300 in case you weren't wondering), ten of the images still aren't DPI 300 enough for Create Space so its still shouting at me. I don't know what else I am supposed to do, short of screaming at people on the street and handing them crumpled copies of the ten comics Create Space doesn't appear to like.

What's not to like?

This one has a foot in it (sidenote: I HATE FEET)