I was half way into the main story, would I miss anything if I skip to the side couple now...

I didn't read the main story, but you can understand the side story without it. there are flashbacks but not everything, about what happens to Do Hyeok during the main story

thank you.

He went to jail for embezzling

with seorim furniture?

I mean why would he do that? his family seems to provide him even though he’s a disappointment

No, he was embezzling through his family’s company for himself and several other nameless people. Because there’s no such thing as “enough money”

That’s too greedy