1. Who comes after the 1st Ippon is awarded?

The loosing player starts the first attack in the next round after the 1st ippon.

2. If a player attacks with a single blue (Crazy Kiai) or a single yellow (Maki waza) card and the other player answers it with a Kamae card?

The original attacking player starts a new attack, because the Kamae is not an attacking card. It can only neutralize an incoming attack. You cannot put an attacking card besides this.