It is highly unlikely the problem is the older rooster's spurs. Look at the legs and feet. Pay attention to the claws as well as the spurs. The problem is probably coming from the immature cockerels claws instead of the rooster's spurs. Once a hen is barebacked the spurs can possibly cut her during mating if the rooster has bad technique or if the hen fights him during the mating act, but generally the only reason you need to remove a rooster's spurs is if they are growing in a way that he can't walk or they are curling around and growing into his legs. It's really rare but some hens can have that kind of problems with their spurs also.
I don't know what your set-up looks like or how many total chickens you have but I think you have three problems. I don't believe in that magic number of 10 hens per rooster solving all problems. I've seen where a smaller ratio works out great too many times to believe in that kind of magic. And I've seen where you still have problems with a larger ratio. Still, I always suggest that you only keep enough roosters to meet your goals. That's not because you are guaranteed problems with more roosters, just that problems are more likely the more roosters you have with the flock. I don't know your goals or why you want all those males but either getting rid of some or isolating some in a bachelor pad is probably a great idea.
A second problem is room. You are right, if they are able to free range these types of behavioral problems are usually a lot less likely or less severe. You have to deal with your Maine winters as well as your great New England summers. I don't know how much room you have but it is highly unlikely throwing a bunch more hens into a small space will solve this problem and will likely lead to other problems caused by overcrowding.
I think the third problem is that you don't have three roosters, you have a rooster and two cockerels. The cockerels hormones are urging them on to be very active and aggressive. The hens and maybe pullets don't respect those bratty adolescents enough to submit to them so the boys are rough. The mature rooster probably isn't rough because he has his hormones more under control. The hens respect him and don't fight him. This does not mean the problems go away when those young brats mature, there are still the other issues. You could see other issues with the mature rooster and these cockerels as they get closer to maturity, especially confined in a small space.
They are probably not going for the smaller hens and pullets, they are probably going for the most submissive. The older or more dominant hens are more likely to be subjective about who they allow to mate. A dominant hen will sometimes beat up on an immature cockerel, even if he is bigger. I find that size isn't all that important, it's more the maturity level and spirit in the individual chicken. My mature hens often run to the dominant rooster when a cockerel starts to pester them and let him deal with junior, but pullets and the less dominant hens often don't.
My recommendation is still going to be the same as most others, especially in winter when space is limited. Reduce the number of males with your flock. Either get rid of them or pen them up so they can't get to the hens and pullets.
