F2p issue (maybe)

You can spend a bunch of crystals on Zuckuss packs and claim the character rewards.

Normally I could finish the pass with galactic challenges...

I've only 2500 crystal so I don't think i'm capable

We had 4x rewards with the last challenge to make up for the missing ones. So if you are not done yet, that means you missed significant tiers on the other ones throughout this episode and wouldn't have gotten there anyway.

I'm in a similar place to you (but even closer to the level 50 reward - I'm at around 48) - you should probably do the same as me and not get a LST. 😉