Would this be a viable build on harder settings?

Any idea of special points layout and perks

Guessing these will be good areas
Big leagues
Demo expert
Locksmith
Lifegiver
Luck tree?

I made a character like this. Designed him to be a bit of a meethead sportsfan. He runs around with a powerfist, a bat and baseball grenades. He started with

Str 4
Perception 4 + 1 from the likely earliest bobble head you'll find.
End 4
Charisma 2+1 from the special book
Intelligence 1
Agility 4
Luck 9

Strength at 4 gives you big league and blacksmith for your melee stuff
Perception 4 for lockpick and can put 1 more point early for demolition expert
Endurance 4 for both the life giver perk but also the chem resistance perk too.
The 3 charisma is for the pretty vital lone wanderer perk
Intelligence 1 something has to be low and i wanted him to be just a I'll fix this problem with booms and punches kinda guy
Agility at 4 cause i wanted the lvl 9 perk that lets you really close the distance in melee but i decided to take my time with this one
Luck at 9 is the biggest. The luck tree is amazing for any build ive found. Though idiot savant is a must take with your 1 intelligence. Basically any of the last 5 perks are fantastic in this tree.

You can go down to 5 luck and spread the extra points where youd like if you dont use vats or crits much. But i find them a great thing to use personally. Also chems are a must if you're a non stealthy close quarters fighter. Psycho-jet is an amazing chem.

I think you're better off just melee. Explosives are situational, and even unupgraded, will rock when you stumble on 5 + enemy cluster. There's only 3 really good melee builds ; a slow and strong one in power armor where you use your action points only to tackle enemies down with the 10 str perk, a sneaky one where you use blitz ( 9 agility ) to sneak attack enemies using vats, and a fist - luck oriented with gun fu ( 10 agi ), tons of luck and the fist perk at 5 where every critical hit paralyze your opponent.

If you wanna go explosive, I suggest you get big guns with it. Rocket launchers and fat man's damage is boosted by both big guns and explosives, making them devastating. I also suggest sneaking around because it's very important to get the jump on others while using explosives. Small areas can be dealt with with a flamer or various mini guns. Just include in your build a way to make caps, like 7 charisma and settlement vendors. Heck, place 5 weapon vendors side by side so you don't need to rest often for your ammo.

Explosives aren't that hard to use

Explosive/melee sounds great. Remember that at higher explosives perks you can make your own explosives

Caps aren't that hard to come by either

But mines aren't good with melee characters. They're good with sniper and sneaky types, so only the grenades are left. I admit cryo grenades with melee is nice though.

Its not always about being top tier or perfectly complimentary to each other. I personally don't care to have sneak characters since they tend to be plain out o.p. in Bethesda games. I'd rather have every fight be a constant tug of war between me and a small army, rather than be batman sneaking up one at a time on my enemies taking them out in the shadows.

That's the nice thing about these games. There isn't a right way to play. If you want to be a Grenadier that works great. Just be sure you've got the health and the plan to make it work. If you want to be batman and snipe in the shadows there's no problem there either. Or anything in between.