HE 3D Delta printer - Firmware/Calibration

This is my first post, so a little bit of background:

I'm from Barcelona, and have been living in Taipei for 4 years now. Last year I bought a HE 3D delta printer in https://www.3dprintersonlinestore.com/ As it turns out, the HE 3D printer is made by Reprap China: http://www.reprap.cn/ (i found that out AFTER purchasing, I've tried to review the printer twice, but the website seems to only allow good or average reviews, not tragically bad ones).

Since this was to be my first printer, and I wanted to get it mostly to experiment with prints before getting a more expensive one, I decided to go for it. I also purchased the auto-calibration option since I thought that, since the deltas seem to have a reputation by being a pain in the arse, the self-calibration would take some of the pain away. I decided to pick a delta instead of a cartesian because they seem to have better precision and be faster at printing, in general terms.

The HE3D seemed to be based in the Kossel/Rostock, so I expected it to have good documentation. Little did I know...

For the assembly, let's just say the instructions were awful and took me much longer than it should have (I'm no expert in 3D printers, but I used to assemble and disassemble electronics for fun, back when most thigns were analogic and difficult to figure out). A couple of pictures taken by phone with some arrows done in MS effing PAINT on top of them. The first time I tried to power it up, the printer almost disassembled itself. After thorough examination (and with a friend helping me), I found out that:

- One motor had two of the cables swapped in relation to the others.
- One motor controller was busted and had to replace it.
- The Bowden tube fell out of the extruder because the fit was lousy.
- All of the motor controllers were in contact with pins on the Arduino board, randomly short-circuiting some of them.

I fixed all those hardware issues, and tried to follow the instructions to flash the firmware on the arduino board. The printer seemed to self-calibrate successfully, but when I tried to print, it turns out the layers weren't flat, but domed (higher on the center of the printing plate, lower on the sides). Tried repeatedly to fix it by changing the rod length, but the custom firmware had most comments in Chinese, and I couldn't follow it to save my life. And as I mentioned, I'm no expert in software, since my skills are mostly related to electronics and mechanics.

After many tries (and a lot of aggravation), I found out that a few parameters (Z offset, for instance) didn't change even if I adjusted them directly on the printer. I tried to flash the firmware again to the original parameters, and I don't know what happened, but now it works even worse than before, being unable to get lower than half height from Repetier, but being able to reach the plate manually from the printer. Autocalibration doesn't change anything on the EPROM, and I don't know what to do. Currently, it's been a year since I acquired it, and I've spent most of my free time (which is not much) to try and get it working, to no avail.

If I could fix the Delta, I have lots of projects in 3D that require immediate printing (the first being a few parts for my 3 year-old daughter's Halloween costume). If I can't, at this point, I'm considering getting a commercial printer with a comprehensive manual that can work almost out of the box, and rip apart the Delta to build something else (and probably replacing the arduino board). That would require an extra expense, almost double that what I paid for the Delta, though.

Any ideas/help? I don't know what else to do.