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Your big problem is damage. With those stats your 12th level damage maxes out at 3d6+31, which averages 41.5.
Meanwhile, a Weapon build Solarian does 6d6+25 which averages to 46.
The problem only gets worse (eventually much worse) as you level. Plus the problem with DR you mention.
You also gain nothing from Solar Armor since you're going with Heavy Armor, and it only works with light.
You're much better off just taking the weapon and saying 'it takes the form of a battle glove' and having a glowing solar fist of death (or glowing solar claws). The flavor remains almost identical, and the mechanics work out much better for you.
And I think you'll do alright (though not great) in starship combat as a gunner provided you bump Dex at 10th (probably instead of Con) and get a Dex boosting item at some point (probably early on).
You might also think about going Dex 12 Cha 14 instead, as that will really help in starship combat and be nice in several other ways.
Oh, also, Deadly Aim is almost always not worth it, and thus probably not worth grabbing. I'd recommend Spellbane instead. Solarian saves tend to not be great due to the abilities they need to focus on not being associated with a Save. Honestly, I might grab this at 3rd and then Weapon Focus at 7th, then skip Improved Unarmed Strike and grab something else at 9th.