In reply to:
When you have power, endurance comes easily, when you have/train only endurance, power comes slowly. It will pay off.
I'm a bit confused about the three finger open, not all rails are the same size of course, and the degree that the campus board overhangs changes things a bit as well. That being said, I basically use the smallest rung I can that allows all four fingers to stay on. Maybe your pinky isn't that long relative to your other fingers to allow this?
If possible, I would suggest finding/buying a rung that allows you to keep four fingers on, open of course. It will be a bit easier but it's safer to disburse the weight between 8 fingers rather than 6. Also, if you find you can do more than 8 reps at this size for at least 7 sets, then add weight, I've gone as high as adding 30lbs on a larger rung before moving to a smaller one.
Currently, the rung I use is just big enough to keep four fingers open on and i do 8 reps with 10lbs on me. sometimes I do 10 reps with no weight.
If it hurts, definately stop doing it. Come back after a few weeks. It shouldn't hurt but I'm guessing it's because the three finger vs four for you.
It does sound like over the three month's, the amount of weight/reps you could do continued to go up, this is a measurable difference, so you know your getting stronger. It doesn't always translate into new climbing grades right away, grades come in waves, you may be stuck at a certain grade for months then blow through 1 2 or 3 grades in a month. It helps when you can measure progress, u know your getting stronger whereas without this you may feel like your not improving even when you are.
Keep doing it at least twice a month even throuhgout your endurance cycle.
Also, when doing weighted bouldering, I find it works best do only climb totally open handed, even on crimp holds and the steeper the better, you'll train body tension like you wouldn't believe and next thing you know, moves that your feet use to pop on they will be sticking.
People have a hard time only climbing open handed in the gym because naturally it's easier to hold a crimp and sometimes a slope in the crimp position, fforce yourself to do it anyway, in time, you will be so strong open, you won't mind anymore.
I only crimp hard maybe once a month, other then that I only open hand and I can still crimp pretty hard.
When you are climbing at your level, many times you get to where you feel run down or you fingers hurt especially when your crimping. If you climb open, your hands will hurt less and as a result you'll be able to climb more often and the cumalative effect over time of climbing more and climbing more at a higher level will pay huge dividends.
Hope this helps.
PS, try climbing on the longest steepest wall at your gym with a weight vest for endurance training, 1 or 2 grades below your bouldering limit, you'll be

after a few weeks. Only open of course.
It is not possible for me to use my baby finger on such a rung. The only way i can get it on their is by half crimping. My ring finger is bigger than my index (ring finger almost same size as middle). I guess that has some baring on it.
----three finger is ok, just make sure to watch for pain, also, I woudn't ever campus more than 1/week, simply because of the repetitive movement and letting it heal, plus 1/week is plenty for pure power training. Even 2/month is good.
I was also rather confused to figure out that my 3 finger open hand dead hang times completely obliterate my 4 finger half crimp dead hang times by quite a big margin. I got a feeling the 1 finger traversing (yes bad advice) has the credit for that. I also tried a few sets with half crimp vs fully open, and fully open was just so much easier even if it was a pinky short. It must have something to do with the way it aligns my arms up, i just get more power in that position. I do not like the idea of leaving out my baby finger, that's partly the reason i added dead hangs after the campusing and do the sets in half crimp to make sure my pinky gets some action. Do you think that is a good call?.
-----I don't recommend ever power triaining crimps, as you get stronger open you will get stronger in crimps too. You can gain crimp strength quickly by power training it buy it's not worth the risk IMO.
I do not want to stop using the campus board, i was hoping it is a sustainable tool to use every few days (no more than twise a week?).
Atm i do not have a real weight vest, just a ruck sack. The weights move around too much and messes with my cog while climbing, its not a problem on the campus tough. Until i can afford a vest i don't think i will continue with weight for bouldering. As an alternative maybe i can try using 2 fingers per hand in your endurance suggestion? middle/index as 1 set and middle ring finger as another?. Leaves the pinky out again ;/ but i can cover that in the campus sessions?.
I don't recommend training 2 fingers ever. Unless you are climbing 14c and training for action directe, it's not worth the risk.
Anyway, cheers.