Technically those aren't cheats.
Headbites: just aim up. A good angle to aim up is at around 45 degrees above the horizon (i.e. from straight ahead). If a human gets too close just aim up further. The lowest you want yo crosshair to be is perhaps 40 degrees or else you will risk biting the torso instead as the human gets into range.
Strafe jumping is a seperate learnable skill that will apply to all aliens, humans to limited extent (stamina) and quake 2/3/champions/WarSow/Xonotic/Reflex Arena etc.
Here is the very basic concept of strafe jumping mathematics. You don't have to leanr it this specific way, but this way will give you the exact angles you need assuming you have unlimited framerate. There was a better website called FunEnder which had the calculations in regards to framerate penalties but I never really looked into their page much and their website was down before I knew it, so I had to re-do some of the calculations and placed them into an excel spreadsheet which you can download (on the page linked).
But in a nutshell, to strafe jump, download this map and paste it inside the folder containing similar pk3 files inside your Unvanquished folder.
Do
in the console by pressing Tilde (~/` key next to the "1" on U.S. standard QWERTY keyboards or between SHIFT and / on older PS/2 windows 95 style keyboards) and press enter. It will start up the map with cheats enabled.
Spawn as dretch on Aliens and ignore the pot holes, go around them and behind a wall there is a blue teleporter, walk into it.
Do
to enable the speedometer.
Go to the right hand lane and align yorself with a wall and just hold W key.
Slowly turn your cmaera into the wall and look down (so you can see the edge between the slippery floor and the wall). Notice yor speed will increase. Turn the camera slowly but just fast enough to maximise your accelerate rate. The angle which you should be using is equivalent to the angles listed in the excel spreadsheet linked above (e.g. if you want to double your max speed, aim 60 degrees to the side from the forward direction) but this will mean yo acceleration is half of your normal air acceleration rate.
Experiment wit ha bit more, and you'll eventually get a feel for it. The slippery effect basically emulates you being in the air because solid slick and air both have no friction. The wall prevents you from turning (as if you are doing it without a wall, you will need to switch directions to maintain an approximate straight path).
It isn't exactly practical to only use the W key (which is the method used in Urban Terror as UrT doesn't allow sprinting diagonally) so in practical use against players to maintain sight of them, it is usualyl advisable to at least, use the W+D key when turning right, and W+A key when turning left. Something that not many people realise, is that it doesn't matter what keys you press as long as your acceleration vector is between 90 degres and is smaller along your acceleration angle perpendicular to your max speed along your movement axis
In a nutshell, that's the basics on how to strafe jump. The funny thing is that despite what many people think, the same mathematics applies to Quake 1 style bunnyhop air physics (which are used in games like Counterstrike: Global Offensive and Natural Selection)
This following video shows me using both styles of Quake 3 and Quake 1 style bunnyhop (albeit in very slow motion as air acceleration with the dretch is much lower than bunnyhop air acceleraton modifiers)
Some defualt mechanics you mentioned:
-The human damage regions can be simplified to three areas: Head (1.5x damage), Torso (1.0x) and Legs (0.5x).
I haven't checked the armour values for light and medium armour in unvanquished yet, but in older Tremulous versions, there was a front, back and side regions in the light armour although the regions didn't necessarily work properly. However in a nutshell, light armour in unvanquished has something like 0.5x modifier, while medium armour 0.4x, and battlesuit 0.3x. This means that as a tyrant dealing 150 damage to the head of a battlesuit containing 334 equivalent health, it will take three hits to knock out a battlesuit and the battlesuit will read 10 hp left or something after struct twice at the head.
In tremulous 1.1 it was 0.4 for helmet light armour(in general) and 0.2 for battlesuit but they had double damage for headshots.
-Marauder doesn't actually have to jump to score a headbite, you can just aim up. But it may be eaiser to just jump over so you don't collide with a player (and in my case with high ping, warp around a lot due to the rather old client prediction system)
-Marauder has 3x or so air acceleration modifier, which means it can accelerate, well, very much faster without the need for walls (And walljumps are bugged because of Tremulous GPP development in regards to a timer bug, and Unvanquished devs in general seem ignorant of it no matter how much I tell them about it)
