To answer your last point, if the enemy jungler managed to snowball so hard, it means that they probably camped a certain lane a lot, which means that
- other lanes should be doing fine in the 1v1
- the jungler didn't manage to farm a lot, so even though they got kills, they are still behind.
At a certain point, after I realize I have a good lead over the enemy jungler, even if they got fed, I always look to be super aggressive. Even if my bot lane is behind, I still get in the face of the enemy jungler and 1v1 them, then proceed to safely gank a lane with the jungler dead and push towers. I steal all their camps and take tower easily.
Basically, removing the X factor from the map is key. You mostly have vision of where the laners are, so if you remove the jungler, you can go anywhere you want and have no one stop you. Once you understand at which point you are stronger, you can then go and invade the enemy very aggressively, look for solo kills etc. If you do that, it doesn't really matter how far ahead the enemy bot lane got.
Let me put it into numbers. I played Graves and I had an enemy jungler (can't remember which one) who was ganking a lot and got some kills / assists in top lane. Meanwhile, I was farming very hard and outpacing him. Eventually, while I was in his jungle, I warded his wolf camp, and I was at his frog. I saw him doing wolves while I had finished frog and when he used all his abilities to clear the camp, I went in and solo killed him. This gave me enough time to secure the blue buff that was spawning about that time etc. At that stage, we were 8 minutes in and I already had 65 cs and 1 kill, while he had something like 1/1/2 and about 35 cs.
At that stage, I was able to easily 1v1 him. This created a lot of pressure, because I placed a lot of vision in the enemy red-side jungle so my vulnerable top lane was able to see if the jungler is close by. Even though he was 0/3, nothing really came out of it, because I had pressure in the entire map and I also managed to kill the top laner in a gank. Essentially, the whole early pressure the enemy jungler applied was neutralized by a solo kill in the jungle and then correct map pressure. And all that happened because
- I was able to power farm a lot
- I was able to be close to my other lanes and prevent ganks. ( I prevented a gank bot lane because I intentionally went to do Krugs to be close).
Now, that's all higher elo theory. But it still works in low elo and it's much easier to do there, because people don't really care about farming and just want to gank, which makes my counterjungling efficiency even higher. More camps for me = more gold and XP. I have a silver smurf and my winrate at Graves and Jarvan is like 90% over 20 games and I just do this powerfarm trick all the time.
The reason why it works is that jungle farm is safe farm. Eventually, you get to outpace everyone. Even if the enemy ADC gets 2 kills early, it won't matter. Jarvan will dunk that ADC and kill them, as soon as he gets Duskblade. And the thing is that if Jarvan farms well early, then that Duskblade won't take long to get. Then, you can proceed to HARD SHUT DOWN the enemy fed member. All you need to do is find good routes.
For example, let's say you're bot side. I start red, then I usually take Raptors, even though a lot of people don't. Then I go Blue, Scuttle, Frog Wolves, back. If there's a gank - countergank option, I will definitely go. Next step is to ignore ANY LANE and run to Krugs. At that point, I know that the enemy jungler will be looking to be bot-side, so me being there is important. After Krugs, I run to his frog / wolves because most of the time, they are up. Even if they are not, I know that the enemy jungler was there, and all that time, my Raptors are back up, probably the bot side Scuttler as well.
See how I manage to stay close to my lanes to prevent counter ganks? Or how I manage my camps to have something up, while I also try to look for aggression? These are the things you need to look out to, because ganking is unreliable; if it fails, you wasted time and pressure. Instead, if you farm, you get stronger and you don't reveal yourself, meaning you have pressure.