I like your design. Go forth and make it happen.
On line length, the optimal line length is somewhere between 70
and 110 characters from what I have read. I found one study here
which didn't turn up a great observable difference in reading
speed or comprehension going from 80 to 110 characters.
http://www.perceptionweb.com/ecvp/ecvp03.pdf (Page 107)
This is a general theme from studies I have seen. Results seem to
vary a bit. Something inside that range appears to be good.
I recommend Bootstrap for building sites, as it was worked well
at my company. The designer here is a big fan of it, and when a
site framework makes him happy, it's got to be pretty good.
As for avoiding the SCSS dependency, I'd say just go for plain
CSS. SCSS and other CSS wrapper languages give you some nice
features, like templates for cross-browser support or variables,
but I don't think they justify the complexity involved in using
them. We've been using SCSS at the company I currently work in,
and so far all I've gotten out of SCSS is that it takes me longer
to go through the feedback loop of making a change to a CSS file
and seeing it happen in the browser, due to the milliseconds it
takes to compile the CSS file. It's really not worth the trouble.
I'll say it again because it's important, go ahead and implement
a new design right away. I look forward to it. Press on with
something to avoid a design by committee scenario from emerging.