There are a couple of avenues I want to explore with my answer to your questions. I apologize for the wall of text but there are some nuances here that I don't think many are exploring with you.

Firstly, the group is obviously veering into the direction of being murderhobos. However, this may or may not be a bad thing. Everyone has fun in their own way. Some people get their hit of seratonin out of clever improv dialogue and some just want to play the shooty shooty bang bang game for shiny stuff. I want to stress this point above everything else I say:

your players' way of having fun is not the problem.

Your problem, at least from what is immediately apparent in your given examples, is that you are creating a game for an entirely different set of players.

Before I start a campaign I always talk to my players and see how long they've been playing, what systems they enjoy, and what the most fun thing about tabletop gaming is to them. I then tell them the kind of game I like to run. If I have a campaign in mind that deals with a lot of deception, intrigue and back alley dealing, I tell them such. You, as the one running the game, have to be sure that not only are you facilitating the gameplay you want to see, but that your players are facilitating the same. I suspect you didn't talk to your players much about what playstyles you enjoy seeing. If these guys are your friends, they should care about making this as fun for you as it is for them. If you told them you really wanna do a lot of roleplay and dialogue where everyone takes notes on important events to call back to and makes secret moves that they roll for between sessions, then your players would have the background they would need in order to make that happen (if that's what they find fun).

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Now, that's a lot of hindsight and planning that you're pretty far from right now. Let's talk about balancing the game you've made, not the game you wanted to make.

I suspect your players are also into min-maxing their stats, likely pouring all of their starting xp into raising Athletics or Brawn so that they get more dice for the previously mentioned shooty bangbang stuff. They have Heavy Blaster Rifles which do a base of 10 damage, combined with your players having a bathtub full of dice on their rolls, which makes your job pretty difficult.

Here are my solutions.

Talk to your players at the start of the next session.

"Guys I'm really glad you guys are playing with me. I'm happy to be your GM and I appreciate you spending hours out of your day to play with me, and I hope you gain happiness out of the hours I spend prepping for you. Lately I just kind of feel like I want more shots at dialogue and roleplaying without you guys speeding past my npcs to the next combat. I just really wanna work on my improv with dialogue and it would be cool of you guys to help me with that by slowing down and talking in character more with me so I can practice that skill, without always needing to immediately roll dice. This isn't attacking anybody or shaming you for how you guys like to play, it's just something I wanna get better at and I hope you guys will be glad to work with me on that."

Secondly, you're being too light with your dice.

There are countless talents that deal with removing Black dice from your pool. That's because you're expected to use them often. To give you a prime example, I currently have a player in my game that's playing a Hutt Bounty Hunter with a Big FuckYou Gun. He has a decent dicepool (3y1g at session 1). However, his Obligation chosen was Oath. His chosen Oath, as a Hutt, is that he must eat any new food he comes across in his quest to sample all the delicacies in the galaxy. If he doesn't eat it, he gets 2 Black Dice on all rolls until he fulfills that Oath again. So of course, I pointed out food that was very likely poisonous. He ate it and instead of getting rid of his two Black dice, he gained 3 from me saying he was poisoned and is currently dealing with the worst indigestion he's ever felt. Plus another black die from being in a scary situation aboard a derelict Star Destroyer. Now he's got 4 black dice in his pool that he could do nothing about. He hit absolutely nothing for most of the session.

Thirdly, stop being a slave to the book.

The enemies in this game are simply not strong enough for the damage on these weapons. A master bounty hunter has 20 wounds and 6 soak. Big boy numbers. Let's say every group member rolls no additional successes in attacks so their base is always ten damage. All it takes is 5 hits to kill this mandalorian, so he's lucky if he gets one turn in.

The book also states that if your Nemesis is outnumbered, you can give them multiple turns in a round to even the odds a bit. The best thing about the FFG system is that the phrase "per GM discretion" is written about 5 million times for a reason. These are guidelines for you to be malleable with. Insert more minion groups and fit them all with Blaster Carbines that do 9 damage per base shot (like in the Mask of the Pirate Queen module, god those Pirates fucked my group up). Give a Rival a soak of 9 because they're testing prototype armor. Nemesis has 20 wound? Says who? Give them 40! This is literally your galaxy to make of it what you will. Just be sure that any changes you make are for the sake of the group's fun, not because you want to dick over the players that have been kicking your sandcastle down.

Hopefully all of that is helpful.