I played as knifer and it's quite decent tbh (although fist-psi build is much better and smoother, and basically the same feel other than cutthroat). So far, I don't think you're "screwed" in any way. I wouldn't pick Intimidation and persuasion unless you knew the skill check places, since those two requires substantial investment that doesn't give you anything special in term of combat. I'd recommend psi 16 will build for "talker" playthrough tbh.
For knives, you don't have to max mechanic everytime you leveled up, since it's not that demanding. I'd recommend leveling your chemistry for a bit and 50 biology for good drugs. Check Grenade wiki to see the required chemistry. I think Frag Grenade MK3 should be good enough until ~16 ish. Ofc you could balls deep on it and get MK5 asap, but makes sure you don't gimped on your melee, dodge and evasion.
As for knives damage, every bit of improvement worth the upgrade imo.Keep in mind that light weapon relies on lots of attack. Use your electric weapon for tough enemies and robot, unless you want to burn through your battery every 2-3 turn. Also, I'd recommend to take Taste for Blood soon, it'll make your build a lot more fun
And I wouldn't recommend maxing pickpocket, 50 should be enough tbh. Get 50 effective throwing, it works wonder