SSF Toxic Rain Trickster: Tuning into Yellow Maps

My SSF TR Trickster is level 78 and just getting into Yellow maps. I'm working on farming a 6L via Porcupine cards, but w/out favored map slots that is slow going, so for now I'm on a 5L.

My biggest question is about what node wheels/areas to focus on. I also have a Cluster gem that could be good, although I'm not 100% sure it is worthwhile.

PoB: https://pastebin.com/469PLgSD

Profile: https://www.pathofexile.com/account/view-profile/OsoMoore/characters

Questions:

1. The Duration Mastery wheel seems like it is largely for bossing to allow more pod DoT's to stack. Is skipping it a good plan for now?

2. Is it worth taking the reservation mastery nodes to pick up Malevolence + another 50% reserve? Right now just running Malevolence + mid-level Vitality.

3. Gear is currently resists + health, with attack speed as 3rd level priority. I have high spell suppression, largely from the tree. Should attack speed be that 3rd priority? I am thinking it helps boss DPS and clear speed, as I have to stop to shoot.

4. Is TR the right tool to clear? I tried Caustic Arrow, but the damage seemed very low.

5. Is it worth filling in my Cluster Gem? Nodes are 12% Chaos dmg, +2 life/int, 2 sockets, Unholy Grace (looks great), and Unwavering Evil (seems OK'ish). Or are there better options on the tree?

I've looked at PoeNinja SSF TR Trickters, and they're all over the place with wheels and clusters, so I'm not sure if I'm missing something important, or there is just a lot of flexiblity.

Thanks for taking a look, I appreciate any input. This is my first SSF, but I have a couple lvl 100's in an EA and an Ice Crasher, so I'm generally familiar with the systems.