I've actually been doing something similar - I do 70 pull-ups total, and attempt to get them done in fewer sets and less rest each week. Then on a different day I do weighted chins.
When it comes to pull-ups I like doing something like this. Switching it up often so that some days I'm doing them without weight and doing more total reps and sometimes doing them weighted.
I have noticed that for me, if I'm doing more than 15 pull-ups in one set, I may as well add more weight or I won't really see any change in my progress. So if I'm doing sets of high reps, I'm only really getting better at doing pull-ups (endurance wise) rather than working on building any mass. It's like doing pushups almost... The more you do, the better you get at doing them, but that's about it.
So if I were wanting to do say, 50 total reps over multiple sets, I get better results doing something like sets of 10 with shorter break periods versus doing as many as I can and doing less reps over the course of several sets.
With weighted pull-ups I get the best results using a weight that will allow 6-8 full range repititions. Occasionally I'll add a lot of weight and do something more like 3-4 full reps.
After you're doing working your back, try adding some weight and just hanging from the bar. Great stretch! Some people add a crap ton of weight doing this but I've tried it and I don't really see much of a point unless you just want to get good at hanging from a bar with a bunch of weight hanging from your waist. You could argue it develops forearm strength but there are more efficient ways to that even.
