Sounds like you are making good progress, and having a little fun cleaning up the kids stuff at the same time. Sometimes it is a little difficult to try and fix stuff from 2500 miles away, but here goes.
First: adjust the wipers so they are snug to the bill hooks. It should take a 10-15 pound pull both ways across the bill hooks. You do not need to check this will a scale pull. They just need to be snug, one hand to move them across. To check this, undo the 3/8 carriage bolt that holds the knotter down and raise it up. As you move up far enough you engage the cam that moves the wiper and you can see how it does across the bill hook. Now comes the tricky part depending on how much adjustment you need. Minor ones can be done on the baler with a hammer. MINOR ONES! Gentle strikes and you will be there. Major adjustments may need to take the wiper off the baler and bend in a vice. Getting them out may not be too easy. Remove the cotter pin on the left side of the knotter frame going through the shaft that it rotates on and slide the knotter to the left to get room between the frame and the intermitent drive gear. Make not of the number of spacers under the pin and whether the knotter was tight up against the cam. If it was loose, there should already be additional shims on the shaft, so add one or two to get it tight when it goes back together. You also need to remove the cotter pin on the top of the wiper so it can drop out. It is tricky and you need to be a little bit of a contortionist to get this done, but it will come out just be inventive and patient. Now you can clamp it in a vice and hammer on it till you get it tight enough.
Second thing to check is the knife that cuts the twine. If this is dull, it will also give you the symptoms you are having, IE not wiping, hanging knots on the bill hooks, and shattering twine. I believe you knives are rivited to the wiper, so it really is most likely you will need to remove the wipers to sharpen them completely. Generally I have found using a file and a little sand paper does the best job over all.
If some one replaced the knotters years ago with much newer ones, you may have the wiper and knife bolted on. If so your job just got a lot easier to make these adjustments. All the JD knotters were the same for the 14t, 214t, 24t, 224t, 336, 346, and the begining of the 327, 337, ans 347, that is you can change them out and use knotter from any of these baler. Parts will vary a little over the years, but the knotters will all fit and work in each of those balers. In the **7 series, that started using split knotters on the shaft and all the **8 balers have these split knotter. (easier to remove knotter completely with out having to remove the shaft and the drive to it.) If you want to while the wiper is out you can remove the rivets on the knives and bolt them on. I have use 1/4-28's with a lock nut to do this. The hole threaded up easily and now I can remove knife with out taking out wiper.
Third, if the above does not solve the problem, loosen up some on the twine disc. Your 100 pound pull is too much period. Look at the length of the little pieces of twine falling out of the knotter (this is normal function, you will not change or stop this) if they are a long inch, disc is good, if they are like 1 1/2 inches disc is toooooooo tight.
Last little note, the pull on the twine out of the twine box, it takes a very light pull. Just a few pounds will do. Some one said 15 pounds, but this is way too tight and will cause problems. These are to be tight enough just to keep the twine from running out from momentum each time a knot is tied , other then that loose is best.
Question for you, have you checked to see if the hay dogs are working with good springs, and have you looked inside the baler when empty to see if the hay resistors are in okay shape? They hay dogs will keep you from making good bales, but not the problems you are having. Bad hay resistors will also give tying problems, but mostly loose bales.
