For a melee build, STR is usually your main stat, as your direct damage output is dependend on it aswell as perks in that particular tree. However, END will also be very helpful for surviving the hits you take whilst approaching your target, and AGI might be of some use too. (Maybe luck but meeeeeeh, RNG...)
The perks you most definetely want to use are:
- STR:
- Big Leagues (obviously)
- Armorer (to keep your PA as protective as possible, you will need that in survival)
- Blacksmith (to boost your melee weapon's efficiency)
- (Pain Train) (certainly helpful in some situations as melee in PA)
- END:
- Toughness (even though you are in PA, you can take a lot of hits until you reach your target, this will increase your survivability)
- (Live Giver) (Not a fan of that one, a plain HP increase, but may be useful to some degree)
- Chem resistant (only if you plan on using chems (like Med-X) a lot in order to make up for your limited possibilities in combat)
- INT:
- Medic (stimpaks are your friend more than ever)
- (Nuclear Physicist) (Since you want to use PA a lot, making the most of your limited fusion core supply (at least early on...) will help you save time/money you can use on other things)
- AGI:
- Blitz (only if you plan on using vats, it will help you to get across larger distances "quickly", saving time and thereby precious health)
For weapons, I'm not really sure about that, I usually go for style rather than being the most effective.
Sledgehammer/Super Hammer tend to be very good, esp. in combination with PA, since the additional STR the PA grants you will greatly increase it's damage. Combined with your base STR + Big Leagues perk, you can deal insane amounts of dmg per hit even on Survival. You won't have to hit as many times, but since your attack speed is much slower you have to make sure to hit, otherwise you are loosing precious time.
Try avoid running in head first, while that may work against small simple groups that are poorly armed and armoured, it will get you killed quickly in other engagements, e.g. against Super Mutants.
Instead, try to flank them and make good use of the terrain, keep in mind that as a melee you will need a direct route to your target. Be aware of your PA's weakness (e.g. against energy based weapons) and try to eliminate the greatest threats first.
Having a backup plan for retreat and refocuse (aka. healing up) also comes in handy, so try to look for potential retreat spots before engaging. Depending on the terrain, you might be able to always only have some of the enemies being able to shoot at you while the others have to switch positions, giving you some time, so avoid being exposed to crossfire whenever possible.
Enemy groups with melees can be quite cool to deal with, since some of them will have to come to you, making it easier (and time saving) for you. Don't forget to block though