So today I was walking down a road when I heard a dragon roar above me, no matter, I pull up my mace and ready myself but then I hear a bear fighting someone. A closer inspection reveals that someone to be Talsgar the Wanderer. I grip my mace tighter and decide I better save Talsgar, the dragon can wait while it's just flying around. So I charge.

Somehow the fight ended up escalating from saving Talsgar from a bear to saving Talsgar from the bear, two bandits, and then the dragon who decided to land soon after I had killed one of the two bandits.

Now to my credit I managed to keep Talsgar safe while slaying all 4 of our foes but somehow in the chaos of the battle I must have got on his bad side since soon after the dragon fell he turned his attention to me and now I have a quicksave with Talsgar the Wanderer beating on his savior screaming death threats and taunts.

I tried putting my weapon up and sheathing it many times to initiate a yield (thanks Bethesda for making a yield system that doesn't seem to work as well as the Oblivion one, I don't even know if it's bugged or if he's just got that much aggression (or whatever that hidden stat was called) that he won't accept yield, there is nothing that tells me which one it is) but it doesn't seem to work and I hardly find it realistic that my strong knight would not be able to open her mouth and ask that weak bard to cease attacking her so I'm trying to find the console command for stopping combat with him but I'm not finding it on the UESP wiki.

Can anyone help me with this please ?

Edit: tried doing just "stopcombat" he sheathes his sword only to pull it up again and attack.

You need to reset his AI state against you or he will keep attacking.

1) you could place a copy of him near you and get rid of the current one. (Get his ID)
2) you could try stopcombat repeatedly it might work
3) you could make him permanently passive (setav Aggression 0)
4) if you know you might hit an NPC and dont want them to become aggressive (SetIgnoreFriendlyHits 1)

These are all oblivion commands but should work here too. (TCAI will also stop all combat but that's not too helpful)

Got tired of waiting so I started to kill him but halfway through he lost his courage and ran away still hostile. No idea where he is right now but I will try your commands if I find him again thanks for the help, I will report back if I find him and your ideas work.

Select the NPC in the console then run this: StopCombat Player
I used it on an NPC in Winterhold after a dragon fight there.