5,000 falls in 35 years? That's a lot of falls. Something like 143 per year. If you are falling every time you climb, then perhaps this sport isn't for you? But seriously, Biron Toss taught me to use the bowline when you go aloft. If this isn't right, what is? The "double" bowline?
Falls. A lot of climbing is just practice, what we call top roping. It is like gymnastics, where you may try a small problem 10 times in a row, falling, you hope, only 9 times. So racking up 15 top rope falls in a day is considered normal when pushing the limit. 143 falls would be 10 Saterdays, and I climbed a lot more than that. Even if you don't fall, you weight the rope every climb, as you are lowered to the ground after finishing. Top roping is like climbing the mast, in that the rope goes from a belay on the ground, over a pair of carabiners (like a pulley), and back to the climber, with little to no slack. Still, one bad knot and you hit the deck. Climbers have these systems dialed in.
When lead climbing (assents from the ground-up, where any fall has some potential for seriousness, over perhaps 1000 pitches, I've taken only a few leader falls on gear, a few more on bolts, none of which were really a surprise to me; I was pushing, knew it, and had good anchors.
Actually, I'm pretty good at this. And I have never so much as skinned a knuckle in a fall, because the rigging was always right.
Knots. A figure-8 is the standard, with several variations in finish. There are 3 troubles with a bowlines; they can loosen with cyclic loading, they can be tied wrong, and they absorb less energy in a fall (a figure-8 absorbs considerable energy while tightening). A figure-8 is practically impossible to tie wrong and obvious if you do. This has to be a knot you can tie in the dark. Additionally, there is always a back-up knot, the primary function of which is to make certain the tail is ling enough.
Shackles. Why would you use something that can open while a load is applied? Such a person should be banned permanently from climbing if they even considered it once. This person is not trainable IMHO. Locking carabiners, though not so good for many marine applications, are made for this. Obviously.
However, don't listen to me. Surf and look for a climbing web site; sailors know sailing, climbers know climbing at a whole nuther level. A accending a mast is trivia.