Dex melee is the one build I haven't played, however, if you're having problems hitting, you should try stunning him or immobilizing him. Easiest way for any character is get 40 psychokinesis and get premeditation. Instant long range stun with 0 AP cost. This won't get through a shield, so throw an emp grenade. There's about 400 other ways of stunning, from tasers, to electroshock pistols, etc etc. You could also use a throwing net and just reload until it hits lol, but that would be pretty lame xD However, you mentioned you went full crafting, so I would go with a taser. You can buy the blueprint from the electricity merchant in junkyard near the protectorate area. Dirty kick is also a good choice for later in the game.
Additionally, dex melee should probably open with stealth and cut-throat. Sure, make sure to focus on unarmed feats, but pick up "the best" other ones as they come. Don't marry yourself to your weapon, you've got two weapon slots you can switch with no AP cost, work with your attributes and skills. Best low perception dex weapons to consider are unarmed, dagger, crossbow, maybe machine gun, and pistols (energy, special, or w2c ammo).
The game is also very openended. A lot of times I actually end up doing that quest at level 16-18 just to let you know. Sometimes I do it at 11.
Lastly, you didn't mention stealth, which should basically be a staple for any light armor character. If you don't have it, it's not necessarily too late, just go full bore into point allocation in your next two levels. Guns may also be needed for heavy armor guys, which you will be facing a lot of. Your dex should make them useful even at low perception against heavy armor, although in most situations you can probably just hit and run them.
As far as leveling, if you're playing oddity, you may sometimes be low level due to bad luck from monster drops and not enough "rummaging": don't leave a barrel unturned
Go to core city and do the first 4 arena levels. Let the other entrants kill the enemies, and pick up the drops. Also, I usually get the plasma sentry disrupter or this quest, as if you're having problems outside, wait until you get inside and have to fight one right next to a level 20 hammer warrior. That quest should get you a level, and is just some silly bots, 'nade the guys outside if you need to. Foundry quests also get you a ton of experience, the beast alone should get you a level and is an easy fight if you bring help (although killing balor is probably not possible with your build due to lack of subterfuge skills :/ I don't really know if you can stop the alarm's from going off without stealth)
Edit: Lastly, crafting is really not that great in this game, just an FYI XD Its (usually) more of a skill dump for whenever you've got nothing better to spend
Kind of a shame they don't mention that, but yeah the lack of throwing and stealth due to crafting skills is what is crippling your character is my guess. Usually dex also go for lock and hack xD
Final note: Forgot to mention as it seems obvious to me after playign the game a lot xD But shoot yourself up with morphine before battle and adrenaline once you start it. The math works out that if you take morphine before taking shots it is always beneficial.
Er.. final final note, since you have crafting, I think the absolute best way to handle it is a stun + a level 4 frag grenade. High level characters get an extreme bonus against frag grenades due to their evasion.
.. but not if they can't dodge
