If you are going to use a Arbalest you are stuck with a one slot weapon, so the Arbalest will be your main weapon, no doubt. As such your build is abit faulty. I'm asuming you mixed up throwing with crossbow and 1h with polearm in your post, that would leave you with too little accuracy in my opinion. Better to sacrifice that strength and power strike for better accuracy as you will be sniping most of the time anyway.
Strength: 15
Agility: 24
Hit points: 54
Iron Flesh: 2
Power Strike: 5
Athletics: 8
Weapon Master: 8
Crossbow: 160-170
Melee: The rest
Taken from DaveUKR's crossbow guide, that can be found here
http://forum.c-rpg.net/index.php/topic,8736.0.htmlI used that build myself with about 80 wpf in 2hander using a Spiked Mace and it worked like a charm. If you "do it right" you shouldn't be stuck in a melee situation that often and if you are you can still fend for yourself decently.
This could also work with a Quarter Staff or a Shortened Spear, but you will most likely have problems with the polearm covering your aim in 3rd person view.
EDIT: Realizing I totally ignored your real question about armor. Light Kuyak, Splinted Leather Greaves over Mail, Leather Gloves and a Nordic Huscarl's Helmet should give you good enough survivability and not rip your wallet apart that much. Feel free to change stuff in the same price range based on what style you want of course.
