boot - Cannot create bootable USB with partitions

I am trying to create a bootable USB for Ubuntu 16.04.02 in a 128GB USB.
I want:

1. Partition for storage (formated as NTFS) of 64 GB accessible from both Windows and Linux


2. Bootable partition (around 2GB)


3. casper-rw partition for persistent storage

The first time I build the bootable USB I used Etcher tool by resin.io. After that I could boot in Ubuntu with the USB but when I tried to use Gparted to resize the partitions an error regarding the block size appeared.
I followed a combination of this answer and this one to create a new GPT and the three partitions. However I was unable to boot with that USB.

When I plug the USB on the computer it freezes completely (the screen remains black without even light since I press the power button and the fan starts accelerating).

I tried to build the image in the second partition with 7z, UNetbootin and Startup disk creator but I always obtained the same result.
I also tried to build the three partitions with mkusb without success.

Thinking that the problem was having the booting partition as the second partition I format again the USB into a single FAT32 partition and built the Live USB with UNetbootin and Startup Disk Creator in there. And I obtained the same problem. I used again the Etcher tool (with the incorrect blocksize) and it is also unable to boot.

I guess something got corrupted in the USB on that process. Do you have any idea on how to solve the problem?

PS. Sorry for the extension of the question, I am quite new in Linux and I didn't want to miss any relevant step.

The problem was in the partition table. Using the default GPT was not working. I used mkusb to build the persistent drive chosing an MSDOS partition table and it worked just fine.