I'm sorry to say but I like most people, do not troubleshoot with proper diagnostic manuals or tools for the most part. I do what I can with my mind and experience, and then go to the code reader or manuals last. I'm sure real mechanics do that also when they have many years of experience, but they start by being forced to use the manuals etc. So we come at it back words most of the time, and it ends in the stereo type of "not diagnosing, but simply replacing parts."
That makes it more expensive often yes, but the one bright spot is that most of my vehicles have always been very old, so almost any replaced part is actually needed in any case. I'm just suggesting don't be mad at yourself much for spending money on various parts, they were very old and really in need of upgrading already.
That being said, your symptoms also point to anther common wear part, the multi function switch. That is now at 26 years of age, a big wear item. My older 73 Ranchero's have a 50 year old electrical system, and tons of parts are super fragile, plus most obsolete. As things get older, it's time to learn which are soon going to be very hard to come by, and buy many of those for your keeper vehicles. I have one of those multi function switches stored someplace, and it's time to expect one or more of my trucks to have problems with those.
Given the issue of the high beam circuit and turn signals, I'd replace that switch also.
