Can someone explain...how to get the most out of lhc after jump

Not sure about this.
I was at Crockies in a party of six, no HS, and I only got about 68k total exp from ones I killed on my own. (I'm lvl 17x, others were mostly low 110-130-ish if i recall)

You're saying 115k total from BW with only HS added to the mix. Kind of doubt it, but I'll have to go check it out later.

Here is my calculation for your situation using the same calculator I wrote for the original scenario:

Crocky base Exp is 48376. I'll assume you are 175 and you have 5 members with you that are each 120. Party Zone in Effect; HS NOT in effect.

Your solo kills - 18414 base + 51559 bonus
Kills you only leech - 8739 base + 24469 bonus

That's a total of just under 70K for your solo kills. You said you were getting about 68k total. If the levels of your party were exact then this would match your findings. you can compute it yourself using my calculator here: Thorr's Party Exp Calculator