Yes, cut the solid line and pull it toward the mountain fold. Do this for all, no matter how small.(Hey I just rhymed,...chirp chirp, HUH!) Anyway, It's not much but may throw you off down the line.
yes you should cut it those cuts keep the shape of the particual peice of card and will add a small hill on that area that is there. it si there for a reason, also make sure you glue it 394 and 122 will keep it in place but the tab will stick out and make it look untidy.
I would recommend that you cut it, then cut a scrap piece of card stock into a patch, and hot glue that patch on the inside to make that a solid connection. It will give you extra strength and keep the resin in check as posted earlier.