1. in build there are arm pen runes either for marks and quints, so dunno why u talk about magic pen :O

2. manamune is often charged very fast and gives both manaboost, stacks well with sheen and passive - its just more late game oriented than early, but here ofc u can skip mana and go for early sheen, however i find manamune useful

3. ok, i've made a research and played with overdrive with golem leashed - its much worse than with powerfist - i even triggered passive - so solution is powerfist>overdrive at lvl 1(at least on blue buff)

4. getting boots b4 wriggles is situational, do whatever suits u best

You really don't need magic pen marks for your jungle (mobs got 0 MR and the only magic damage of your ganks is 60 from your grab until lvl6). So get armor pen marks and other quints, like flat AD, movespeed, health, whatever suits you most.
Also manamune after wriggles is ridiculous - skip it entirely, you won't be able to charge it to full anyway and just sank a ton of money a jungler doesn't have into it. Rush sheen after wriggles and tier2 boots straight away. If you build a glacial shroud anyway afterwards there should be no mana problems at all (you also have bluebuff).
You will want boots1 before finishing wriggles btw, else your ganks suck.
And why don't you get overdrive @lvl1 instead of 2? 30% atkspd buff seems to do more than a double-hit every 9 seconds?

Well written. It can be viable if you do not piss of your mates in champion select, (like i do coff coff).

Keep up the good work mate!
Thumbs UP!