StringHelper.java lines 33, 35, 53 😄 and this http://i.imgur.com/1zVrwxS.jpg
Also, why not to use vanilla Tinkers Construct names? For StringHelper.java stuff.
Some more stuff:

1. Weight string should have %s tag. Additionally it should have "Arrow" string because I need to modify word "Arrow" and swap it with word "Weight".
2. Hardcoded "Bow" string should have %s tag too.
3. tictooltips.tool.effective.durability=Effective %s should have independent "Durability" string because I need write "Durability" lowercase.

You seems to not noticed "Some more stuff:" 😄

Whoops, didn't see the edit before I committed.

1. Not sure how I should fix this one yet. Note, though, that the arrow string comes from item.InfiTool.Arrow.name.
2. I simply removed the "Bow" part of those strings. They weren't really necessary and they would be somewhat of a pain to make them work right with localization.
3. You can just replace that whole string with your own; it doesn't have to have a %s in it. For example, tictooltips.tool.effective.durability=Effective durability: would work.

Ok. So, point 1 still a problem. Maybe it possible to add this string into TiC Tooltips?