In addition to what chickentooth suggested, I would also isolate him in your garage (if you have one) or in a shed - someplace that he's not around the hens. I built what my husband refers to as a "hospital box", which is a large cardboard box filled with shavings. I put water and a feeder in one end of it, and the sick chicken in the other. I then put the box in the garage, where it's warm (we have a brooder with a couple heat lamps in there, I set the box right next to it so some of the heat from the lamps goes in the box too). If the chicken is really sick, we check him into the inside hospital (our bathroom shower stall). The chickens seem to not mind the being in the box at all, in fact, I think they prefer it because it's closed in a safe for them. If he's trying to get out of the box (which is actually a good sign, I would think) maybe you could put him in a large dog kennel.
I know you said you're having trouble catching him. The safest way to pick up an angry, aggressive rooster is to pick him up off of the roost at night, or off of the ground when it's dark. I have a Polish Crested that has a love/hate relationship with me, and he has spurred me several times (the last time resulted in a tetnus shot for me). They seem to calm down quite a bit after dark, maybe because they can't see you coming? If you can't wait, then chasing him into a corner and scooping him up is second best. You want to catch him as quickly as you can, because being chased around is stressful for him, especially if he's already sick. I've never tried it, but I've seen a large "poultry hook" for sale to catch them, similar principle to that stick lifeguards have to fish people out of the pool. You could try throwing a blanket over him, too.
Once he's better, I would suggest working with him to establish your dominance over him. Basically you want to teach him that you're the dominant alpha rooster, not him. You can do this by picking him up, holding him for a bit, then putting him down. Try not to back away from him if he flaps his wings at you, or fluffs his feathers up at you. Take a few steps forward at him when he does this. (You can even flap the sides your shirt at him, if you have one unbuttoned - it looks like you have wings too). If you are feeling especially confident, and you have good balance, you can try shaking your boot in his face. (Just be ready for him to try and attack your boot, then just shake him off of it). Eventually he should stop attacking you, although it might take awhile. With my rooster, Sean Paul, it took about six months of this before I felt safe turning my back on him - and I still only half trust him! After having lived through my battle with Sean Paul, I now spend A LOT of extra time picking up and holding my chicks as soon as I realize they're roosters.