I like the first 3 zeta choices. The next three I'm hesitant on. KRU is a good lead and you need to have multiple good leads for events like GAC. But it's also necessary to get that one killer squad together for Arena, GAC and TW. Bastila-led Jedi obviously isn't doing it for you. I think I like R2's Number Crunch a bit better than KRU's leadership for you right now, and KRU will come soon enough.
Your fleet is doing better than your squad in Arena, but either it's getting ready to fall or you have a very easy shard. Your fleet has no synergies at all. Whatever the reason for your current fleet arena position, you have to improve that right away. I think it's time for you to gear Ackbar and then go after Bounty Hunters in a very serious way. You need their ships and IG-88 and Bossk all at 7*. Then you need to give Dengar, Bossk, Boba, + 2 others (but not IG-88) some serious gear. Like g11 at least. Chewy is going to completely transform your Rebels, and the MilFalc is going to completely transform your fleet.
In the meantime, you should be buying all the ship shards you can get from GW store. Before you can complete rebels, you might actually manage to get useful GeoSpy and Sun Fac ships, which would allow you to start your 3 Geonosians and keep using Thrawn for a bit. But if you can't get a good Geo squad together before you improve your Ackbar, you should probably be using Ackbar + Rebels as your fleet. Then make sure that Phantom II always starts as a reinforcement. It has the best reinforcement ability in the game, and as soon as you get a working tank in your starting 3, the ability to get your ships up to 5 while the other team is stuck at 3 (brought in one reinforcement, but lost 1 ship to your concentrated fire) quickly becomes an overwhelming advantage. KRU's ship is still good to have even without synergy, but you have a GREAT Anakin and no Anakin ship. Anakin's ship would be better here, b/c it land's target lock, which allows you to start Ackbar (L), Biggs + Ghost + Anakin (starting fighters), use Biggs as a self-healing tank while dealing decent damage, then bring in Phantom II and ramp up the pressure with Vader's TIE and KRU as your next reinforcements up.
Meanwhile, Starting Ackbar (L), Biggs + Vader + Ghost and bringing Phantom II, then Silencer off the bench is still good. Your Vader is going to work just like Anakin (no surprise, since they're the same person in different ships) - the ship has 100% accuracy with its basic and inflicts target lock. Every target lock heals Biggs and refreshes Biggs' taunt, making it possible to keep all 3 starting ships alive until Phantom II can arrive to help out.
You have Cassian's U-Wing, so I would also drop as much gear as you can on the Cassian U-Wing crew (Cassian, Jyn, & K-2s0). When the U-Wing is ready, that's your 2nd reinforcement, right after Phantom II. The synergy is amazing and the reinforcement bonus for the U-Wing is great. (But you have to max it out)
You should be extremely careful how you use your ship reinforcement materials. Only use them on ships with the very best reinforcement abilities (there are many that are junk) and even then, only if the ship fits in your arena team and you know the ship will be coming off the bench. For instance, the Hound's Tooth ship is a great ship that will always be in your starting lineup, so there's no chance to activate its reinforcement ability. Even if its reinforcement ability was fantastic, leveling it up would be a waste since it would never get a chance to use that ability.
As for spending in Cantina store, I like two remaining characters: Hoth Rebel Scout and Old Daka. Probably Hoth Rebel Scout first because of how useful it is in Hoth TB and how useless it is if you get it late in the game. Do it now while it can still help you.
As for spending in Arena store, you need: Cassian, Ventress, IG-88, Nute Gunray, & HK-47 ... probably in that order.
Nute Gunray and Ventress can both be very helpful in getting Padme. but you're more than halfway to finishing Cassian, so I'd do that as part of your fleet improvement plan. Nute Gunray is the one character whose order I'm most uncertain about. You need to collect the bounty hunters for Chewy and the Millennium Falcon, so IG-88 is a must. But you have to collect the Hound's Tooth which is a slow farm, so you might be able to finish Nute Gunray before you need to pick up IG-88 shards. Whether or not to move Nute Gunray up the priority list is up to you, and depends on where you are on your other farms. That's probably not a decision I can help you with. But I can definitely say that Nute Gunray's leadership is probably the single best one for the Padme event, and you should get him when you can.
Remember, it's much easier to get top 20 in Fleet arena than Squad arena, and getting a steady income of crystals from fleet arena makes all your other farming efforts go faster. So even though it seems like a waste to improve a character like IG-88 that you only need for fleet events (not even fleet arena), spending time and gear on IG-88 and other fleet-important characters (like Cassian) right now, won't cost you anything in long-term development, because 6 months after you're done, you've gotten back everything you invested in those two characters from all the extra crystals you gained. Short term? Sure it's a sacrifice. In about 8-9 months? It's no difference. In about 12 months and after that? You're at a big advantage compared to ignoring fleet.