If you are referring to the Good Samaritan Act, it will protect from liability those who attempt to intervene into a situation with the intent, in good faith, to help the person or persons in distress. If you are qualified and don't intervene, you can be found liable. If you are qualified and botch the attempt resulting in injury or death, you can be found at fault. If you are not qualified but you attempt to assist, you're supposed to be protected. There are small nuances in addition to be aware of. If you are not qualified and decide to use equipment you're not trained on and this results in injury or death, yes, you could be found liable for those injuries and/or death. BUT, I can't picture a situation in which a blood pressure cuff and/or a stethoscope could be tools used to cause injury or death. You're much less likely to cause injury using a BP cuff as a tourniquet than if you used a piece of rope. I like BP cuffs as tourniquets. And it just so happens, the BP cuff and stethoscope have other uses, should you wish to utilize these additional uses. It doesn't take 4 years of med school to learn how to take a blood pressure. Monitoring a blood pressure on a victim, miles away from help with the knowledge that you are many hours or even days away from help, can help you determine if the victim is beginning to show signs of shock. You can, contrary to your statement above, treat for shock (a killer!) in the field. Elevate the feet, keep the victim warm, if they're able to take liquids you should be sure to keep them hydrated. These are all things you can find online and are non-invasive, are simple to do and can save a life, won't get you into legal trouble and, if you choose to not do these things, you or your mate could die. Better to have the tools and not need them. The same thing goes for suturing. It's not going to make the victim's situation worse, so why not do it? These are not things you would do if you are close to help, only if it's otherwise.
And a book I would recommend is the EMT manual. You can pick it up at your local junior college or technical school's book store. (for outofmemory)
What kind of a scar do you think your friend would end up with if your 3 or 4 days from help and don't suture it up? In either case the docs can re-open and re-suture when you get back, in most cases. But suturing helps keep out debris, control bleeding and in many cases ease pain. Suturing is not rocket science. I do agree with you that glue and steri strips are useful tools. But for life threatening soft tissue injuries steri strips are useless. You could combine suturing and glue in some cases. But getting glue into a deep gash rather that just gluing the surface together can cause tissue necrosis (death). I also agree with your comments on the newer clotting agents out there now. The problem with them is that they are expensive compared to other techniques, they have an expiration date after which they may lose their ability. But, I would definitely have some in my kit if I was going out into the boonies.
Irrigation of wounds with water or saline that isn't sterile is not useless. As I stated before, it's acceptable if it's good enough that you'd drink it. Of course sterile is preferred. But it's expensive and has an expiration date. You're going to be put onto a massive course of antibiotics regardless of which you use. I had never thought of adding a few drops of iodine to the water. Sounds like that would be a good idea. Water purification pills and/or boiling is an option if you have the time.
Lets not forget the original reason for this discussion. No help available for a significant length of time and a victim with life threatening injuries.