Sword and Board is tough damage-wise. Also, it's worth noting that he's invested a lot in defense, and virtually nothing into offense with the current build, so not being a damage machine is not surprising.
Probably the most effective S&B Paladin damage dealing is to use the ACFs to grab Inspire Courage, Words of Creation, and Dragonfire Inspiration. S&B can be turned effectively into TWF with a few feats, and there you go. However, with the Hellreaver levels, I don't know if that will be effective enough.
Power Attack is always a great, relatively low investment way to go, though. The "board" thing makes it more difficult since you're not using 2 hands with your weapon, so it ends up being really sub-par. I admit that reading Uncanny Blow kind of makes my head hurt. But, assuming it lets you fake holding a one-handed exotic melee weapon in two hands -- which is a totally reasonable ability by the by -- then that's a godsend.
The other thing he might think about doing is finding big bonuses to hit to help fuel his Power Attack. The usual charger shenanigans seem a bit at odds with the concept as they involve sacrificing AC -- and therefore what seems to be his tankiness -- for damage. I'd suggest looking into possibly swapping the Protection Devotion for Law Devotion, which gives him a great tactical option. Unless the party really benefits from the AC buff. You can also look into Divine Might: it burns through turn attempts quickly, but it gets the job done if he's got the Charisma for it. And, if memory serves, Hellreaver gets some decent attack bonuses with their special abilities (and there's a feat that reduces ability damage, it's in XPH but I'm away from my books right now, but that should allow him to refuel those abilities easily).
I'd also ditch Extra Smite: unless you've seriously house ruled it (e.g., using Pathfinder's Paladin smite), I usually find whatever you gain from that to not be worth it. Even Extra Turning might be great with all the divine feats.
And, he should totally fork over some XP for a badass sword. Or, even take something like the Ancestral Relic feat. You get XP quickly, so he should just get over it. It's silly that you have to spend XP to like play the game effectively, but it is what it is. Alternatively, I think there are some GP ways to circumvent XP costs, but I haven't played with XP costs in years, so I'll leave those to somebody else.
I've rambled a bit already, but one final note. Are enemies avoiding him, or is he just not feeling like he's hitting hard enough? It sounded like the latter, but at some tables tanky characters end up feeling useless b/c the enemies never let them tank. If that's the case, then he should invest in some lockdown abilities: like Lockdown and the Mage Slayer line. Come to think of it, the Mage Slayer feats, especially the latter ones, might be a lot of fun for this type of character. Sure, it doesn't help his damage, but spectacularly shutting down all of the enemy's abilities with a swing of his mighty sword is both impressive and flavorful. He might also consider finishing out with Witch Slayer.
