The thing to think about with these "ancient" NPC's, is that in all this time nothing has been able to kill them, and they've been adventuring for years (read MAX level).
So IMO all of the still living supermutants should be tougher than FO3's Reavers/ and or Albinos (including Marcus); and Marcus should look on the PC practically as a child.
I guess that's because of RPG logic.
Hell, I hardly think that max level is 30, it's just what the PC is expected to learn during the games time.
It's expected that the player should complete fallout 3 during one year which without broken steel = 20 lvls.
But let's take 2 years = 20 levels.
It's been 95 years since he met Jacob which means he could be able to have reached lvl 950, in his current age that's
his max level.
But I don't think he is at max I think he's just half way through but whatever, let's say lvl 400.
Fawkes has 8 in endurance so I'm going to set Marcus' to 7 because I can't find his SPECIAL.
Base health is 100 in fallout 3 with x20 END, his base health would be 240, 399 levels = 3990 health, so Marcus total amount of hit points would be 4230 HP.
He would have by fallout 3's standard 399 perks or by new vegas' standards 200 perks.
He would have maxed out all stats several times over.
>_>
Marcus should actually be a god...
But again, RPG logic, he will probably be worse than The Courier at mid level.
Even if someone has a statistic that would scale this one down significantly Marcus would still be god material.
He's over lvl 100 IMO.
If he were at max level he would have
9730HP, actually, just to avoid the "IT*S OVER 9000!!!!" meme I'm sure he took the "It's not over 9000..." perk which set his max health to always be 8999.