PX4 Partitions and Wiped OS

Problem: PX4 did not have enough storage space and majority of space (8.5 GB / 11GB) consumed by OS. Sub-Problem: It now does not boot, at all.

Attempted Solution: Wiped OS, installed ubuntu 18.04 on (hd1,msdos6) partition. However,when booting, it enters the GRUB menu. I set linux (hd1,msdos6)/vmlinuz root=/dev/sda1, initrd (hd1,msdos6)/initrd.img, and then boot. Vmlinuz and initrd.img exist in this partition. Boot fails and enters startup kernel, which fails upon entering further commands there.
Goal: get lightweight version of ubuntu 18.04 back on drone plz

I have since tried:
Reinstalling OS on same partition (from flashdrive I have successfully installed the same OS on other systems)
Trying to boot from Grub

Sub Questions: There are currently 7 partitions on the drone. Can I combine them all into one or does the drone need these partitions to fly? I think the install is separating boot into one of the other partitions upon install.

Thank you