you used position: fixed; which means the sidebar will always be there depending on the window size. you could try changing it to position: absolute;
I said previously that this was my last tumbler post but THIS IS MY LAST TUMBLER POST.
border-left: 1px solid #BE6464;
they never come back or the problem doesn't ever get resolved, but I feel bad to let there questions go unanswered. so is it really worth answering? I can't decide. someone decide for me
EDIT: you want the sidebar fixed, but you want the content "endless"? I highly doubt you will be able to do this with the layout that is set out. The layout was designed for a page number