Can great ECs make up for low grades?

So this is fairly tough to say definitively as all of the schools under 35% will likely auto-reject you. Then the schools from 35-70% give huge weight to academic capability first and foremost. I would say that they nullify leading to rec-letters and essays and possibly a few other data points leading to your decision and the higher admit rate they have the more likely it is. Then the schools over 70% will make a decision purely on academic capabilities but the bar is low so to speak. You can still likely get into really good schools like KS St for example so don't despair.

Also Id really really encourage you to take the SAT/ACT to showcase you don't "suck" academically.

Hope this helps and feel free to ask for clarification!

PS: The % are the admit rates if that's not clear.

At some schools yes. Even if you didn't have good ECs it's not like you wouldn't be able to get into college with a 3.0, and with great ECs you will likely have a much better shot at schools you would not have been able to get into without them. I don't know what school you are specifically looking at, some are going to care more about ECs than others. There are other factors that can influence what schools will accept you such as SAT/ACT score, teacher recommendations, if there are any specific circumstances that affected your grades, If your grades improved over time, etc. Hope this helps, good luck with your future endeavors!