1- Suicide bombing: you already know this. You stuff your car's front bumper with stickies and kamikaze against the douche. I'll simply suggest you to use an Elegy, since you can get it free and you don't pay insurance for it when you destroy it (last time I checked. Dunno if they changed it. The car is still free, though).
When being gang spawn killed you don't get time to get a car, and OP was in the middle of nowhere, so no cars there anyway.
2- Predict your enemies moves - car version: you see a white dot going down the street you are at mad speed. Must be a douche in a Chrentorno. Cover the road with stickies and stay behind them (don't stay near them, you want to kill the douche without killing yourself). Douche goes over the stickies - boom. You waste 10k, but it's worth.
Again, gang spawn killing in the middle of nowhere. Blips are irrelevant as every one of them is a few seconds drive away and is coming for you, now.
3- Predict your enemies moves - on foot version: Take cover on corner A. Douche takes cover on corner B. Place sticky on A and proceed to C. Douche goes to A - boom. Rinse and repeat. Works with multiple douches at the same time, just be calm and use your mini map a lot. The mini map. Use it.
Enemy moves predicted. They're a few seconds away, in a car, with their friends who are also in cars and they're all coming directly for the OP.