First of all, I never have played goblins myself, but I have played quite a bit mono red and other tribal decks in vintage.
Manabase: 4 fetchs and 2 bloods are only 6 black mana sources. That's under 60% of having one in your starting hand, and after 3 or 4 draws you will still be without black mana if needed.
Goblins choices: I only "dislike" war marshal, I find him under level.
Simians: Having 2 mana in starting hand is way better than having 1, but it's a risky play unless the played card makes a huge difference.
Sideboard: I used pyrokinesis some years ago, but I think that mentor has changed it into a bad card. Playing black you can go from engineered plague to antitokens, or play sulfur elementals. Mentor seems highly favoured so I think this is a must.
I think that pithing is nothing special in this list. It's unlikely that you are boarding this in against mud or non-tezz blue deck. Rakdos charm (props to @AmbivalentDuck) could help against dredge and mud, as you are playing really low MUD hate
As said, probably a pillar effect is better than thorn most of the time.
Playing red opens space for blood moon. While you lose cavern and black, your opponent will suffer more than you. Just an option to test.
oath is not covered by anything outside earwig.
Overall I think the idea is to play a soft lock with null rod and wastes while hitting as hard as possible. Earwig and silver bullets help with the plan. Seems a good idea against slow decks, but I don't know how slow is the format right now.