You should always have a bicycle with you so you can loot cities without losing any fuel. Looting cities like this might be slow but it takes away the risk of running out of fuel. I made a UAZ-469(12L/100km) when I was somewhere around Kazan. I had like 400L of fuel and now I'm at Tyumen and I have 600L of fuel. As I said it might be slow but it definetly pays off. And for diesel; I wouldn't bother picking it up. I just make a marker on the place that I found it and save it for when I get an electric car.
Salt, sugar and tape can all be found in intact houses. Using the method above you will easily be able to stack up on those.
Cement, sulfur and potassium nitrate can be found in costruction sites, level 1, 2 or 3 bandit forts, department stores and universities. As the time goes you will be able to have a lot of those it's just not one of those things that you can get easily.
Now for the enemies. If you are in a town I wouldn't bother fighting boars and bears early on. You should only fight boars when you need food(outside of towns) and fight bears when you need bones or animal skin(also only outside of towns). I am usually able to kill them with my "hunting setup". It consists of a handmade shotgun, a makarov and a knife. I do have iron armor so if you have highway or leather I would recommend using an AK. And now for bandits. You should easily be able to kill level 1 forts with the "hunting setup" and level 2 and 3 forts shouldn't be a problem with iron armor and an SVD(you get it from completing the Searching for truth quest). An SVD is the most efficiant because it only uses 1 rifle bullet per shot and it can deal up to 250 damage to armored and 150 to non armored bandits(depends on your firearms level). If you don't have iron armor or better i wouldn't bother fighting level 2+ forts.
So yeah that's pretty much it! Good luck!