Check vendors (most NPCs can be traded with) for food and potions. There are healing spells, as well, including one in Man At Arms.

There are spells to stop damage over time (Jahan starts with Rain, for example), or heal faster than damage is taken.

Enemies do not always attack the weakest character, but that is generally one of the better options. This is the first I've seen someone complain that enemy AI is too good. Maybe you could try a lower difficulty level.

Click on animals when you are farther away, rather than trying to get close first and then click on them.

Don't let enemies kite you.
Really, that is a simple tactic to kill enemies in games that don't have the scripted AI or game mechanic to prevent it. You should have the pattern recognition skills to realize chasing ranged opponents repeatedly will not help if you can not catch up to them.
You can delay your turn (to the end of the current turn order), and you can pass your turn and save unused AP (up to your maximum). There are multiple skills and spells which can let you move around without running after ranged opponents, and you can move behind cover or away, as well. Melee opponents can use grenades when they want some ranged damage (a point in Scoundrel is required to get a talent to throw grenades accurately), or pick up spells that don't require a high intelligence to use effectively.