Buy what you like, but points being old does not make the spark disappear. Nor do brushes of different lengths. If you disturbed the points and had no more spark, you may have made the spring short out, or got grease between the points. You may have let an HT brush fall out of the pickup. Is the earth brush (or brushes) in place?
It's hard to think of something that would cause a good running bike to start pinking. Why would the timing advance itself? Timing slips, but usually goes retarded. Pinking can be caused by weak mixture, as said above. A mixture which becomes weak in service can be caused by a manifold air leak. Test by spraying WD40 at the joints in the manifold while it's idling.
As someone mentioned, too much coke in the combustion chamber can cause pinking. Not a common problem nowadays.
Sounds like something is fouling your plugs, if new plugs help for a while. Blocked air filter causing richness and sooting of the plugs? Did the bike start smoking?