You keep from getting your ribs broken by keeping your elbows tucked, which is mostly where they should be anyway if you're in anything resembling a boxing stance.
Beeing only a blue belt, fighting under "pressure" is something I am currently struggling with finding a good strategy for.
To handle single 1-2-3 combinations is farily easy, but if something comes at you and is flooding with techniques and one focuses on blocking I find it's easy to tuck up and become passive. Also your elbows can not be all over the same same time. If you focus on protecting your front ribs and solar plexus, your back ribs are exposed to hooks. Also lowering your hands, then your head is exposed (to either kicks or punches, depending on what the style allows).
I am now leaning towards that in such situations counter with force is best defence, but without experience I am not comfortable doing that under pressure as I feel the chances of accidently hitting someone in the face is high. In kyokushing we don't do that, as it's bare knuckled fightinh, but in the heat every now and then you touch the chin of the opponent. As I might aim for the collarbone as he happens to move, or my fist bounces as he blocks.
This is what I am struggling with atm. Going in aggresive counter mode, would probalby work, but is not recommended in the dojo as one has poor control and chances of accidents is high. Our sempais tells me this comes after alot of fighting experience only. So as a beginner that is farily strong, i must hold back until my control is at the level of my strenght, and that will probably take years.
I am sometimes told to go harder, like "your strong", don't back down, but its because i don't have enough control to "safely" counter aggresively. Hurting your partner is quite embarassing.