Hybrid Set

I'm building up to my hybrid sword/gunner set with mixed resistances. Currently, I'm at this 3* set:
Woven Snakebite Shade Helm
Dusker Coat
Twisted Targe
Nightblade
Antigua
My goal is to reach this:
Sacred Snakebite Shade Helm
Vog Cub Coat
Barbarous Thorn Shield
Archeron
Argent Peacemaker
Anyone have any advice for tweaks or alterations?

Antiguas are pretty weak and won't really stand their own ground properly vs Undead and Fiends. Consider getting a piercing weapon to accompany these two. Blitz Needle is really good later on in the game once you start playing Firestorm Citadel and Final Flourish is a very good choice as it's a generally good sword, especially useful for fighting those pesky Fiends.
Another thing you might want to do is switch out the Argent Peacemaker for a more powerful elemental gun such as Arcana or an Alchemer, preferably Storm Driver or Nova Driver.
Lastly, that helmet is not good. It will nullify your fire protection from the Vog Cub Armor while giving you some poison, which happens to be among the least useful resistances in the game. If you really want a helmet in this line, I suggest you get a Falcon item instead. That said, I don't recommend this type of armour at all. Instead, you can get Gunslinger line armours which have no drawbacks and about as good offensive bonuses or Chaos which gives a lot of universal bonuses, but has more resistance drawbacks.

I would recommend on getting the shock+shadow gunner armor over the poison+shadow one. Poison+freeze resistances are OK, but not as fantastic as shock+fire ones. Canceling out the fire resist from vog is a bad idea, using freeze as a dump stat is a good idea- especially when you'll eventually be getting a black kat set if you stay long enough for that.
Your weapons are fine, but I would look into crafting a wider number of them for a wider number of situations and prioritizing an alchemer or autogun line weapon over antigua.

I agree with the comments posted thus far. See also my detailed sword guide --- especially the section on Mixing Weapon Types.
The gunner armors are varied enough that you could just as easily get more useful status resistance, such as shock or fire. Consider also Shadowsun.
Argent Peacemaker is easy to use. That's why a lot of players recommend it as a sworder sidearm. They assume that sworders can't be bothered to learn how to use guns properly. But if you are willing to learn how to use your gun, then I recommend Nova/Storm for better damage and more fun. Or obviously Blitz Needle if you're into Vanaduke.

Making a Snarbolax Coat would go FAR better with that helm choice.
Matching up defenses and status resists on sets if key to survival. You should have at least one set to deal with each type of damage resist.
One pierce set, one shadow set, one elemental set. Most levels only have one type of damage and almost no variation of status in a level. (monster crates, stun monsters, mecha knight spasms can all deal an added status if present). Maxing your status resist for each situation is best.
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Suggested Gun/Sword Hybrid armor sets:
Perfect Seerus mask and Vog Cub Coat
Sacred Snakebite/Grizzly Shade Helm and Snarbolax Coat
Sacred Grizzly Pathfinder Helm and Skolver
All these offer good defense and good offense. Moderate Risk moderate reward, good for feeling out the game, and surviving all while being able to deal a very respectable amount of damage
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As for weapons:
Divine Avenger is a powerful weapon, it's charge attack is wide, easy to aim, and deals great damage and knockback. (useful in FSC and ICMF)
Blitz Needle is considered a must for all players. As you progress you will be given a 4 star recipe as a mission reward. The charge has enough power to OHKO a Trojan but it is risky to use and leaves you open to attack.
The Flourish and BTB are both great weapons when dealing with fiends, the flourish charge has devastating power while the BTB is easier to aim and use.
The AP you have is OP but the Elemental alchemers are nice choices too.
Fire has good power and works well as a "fire and forget weapon"
Ice makes it easy to charge up sword attacks for more damage
Shock provides a middle ground for them all
The Prismatech has just more raw power.
The Permafroster is a good shadow weapon that can be used to control enemies and allow for charge attack setup.
You are going to be in the arcade for a while if you are planning on using that gunner helm, but I discourage you trying to make a jack of all trade set. Spreading out the weapon bonuses like this won't do you any good. Low ASI and low damage bonus are hardly noticeable on any guns and acheron is not really an ASI reliant sword, If I were you, I will turn my dusker coat into a skolver coat for the med sword damage, or heck, snarby coat.
So yeah, I think you are at a cross road here, gun or sword, pick one that you want to be specialized in and focus all of your armors onto that weapon type.