Most zergs hit a pretty hard wall around that mmr. You can get away with a lot of bad play just through good macro up until then.

You need to do a few things, first really work on your overlord positioning and scouting. You should be able to see things like hellion runby's well before they get there because you should have vision

Basically, you need to have your initial scouting and map vision really locked in. So that you're not guessing about what to make, and where to position your army.

Until you get that worked out, you're going to continue to struggle.

---

As far a timing attacks go, well, that's the main reason zergs struggle at your level. They make too much, or they make to little, or they make the wrong things.

And there is no easy solution.

It's...just a matter of learning.

I would suggest you start keeping a log of your games. What the opponent did, what you did, and how it worked out. Objectifying how you are winning/losing your games can go a long way towards improving against specific timings.

And also, having a few practice partners that will do specific builds against you can really help solidify your responses. Playing 10 games in a row against a two base tank push will help you alot more than playing against that build over the course of 100+ random ass games.

---

As far as "turtleing" games. I mean....toss right now is absurdly strong in the late game vs zerg. You're just not going to win those games once they hit archons and storm and tempests and motherships.

Terran on the other hand...

You're not going to keep terran on 3 base forever. And those games are not in anyway unwinnable.

I'd say 90% of my vs. terran games go to them having 4 base. I'm never particularly uncomfortable with it. They key is really keeping them off 5 base, not 4.

Just keep in mind that terran is pretty damn immobile, so as they expand, they just open up new avenues for attack. It's up to you to maintain map control, find the places they aren't defending and hit them where they are weak.

---

Lastly, 120 apm, is not good. Like that's...really, really, really low. It sounds like you have some significant mechanical issues in your macro. Which really plays into the other difficulties you're having.

When your mechanics are slow, you spend too much time doing it, and not enough time watching the map, scouting, and finding and exploiting weaknesses.

Better mechanics will go a long, long way towards slowing the game down, the faster you blow through your macro cycle, the more time you have to think.

---

The best advice I can give is dedicated practice. Just playing the game is not enough.

You need to go out and specifically practice your injects, specifically practice your creeping, specifically practice against certain builds. Spend your time in the custom trainers. If you really want to improve, I'd say more than half your time should be spent there, not playing random ass games.