First, a general update:
USB does work, but the USB-attached ethernet AX88772B doesn't. I suspect a GPIO needs flipping or a driver bug.
The I.MX ethernet is now working reliably on the latest kernels, but I'm not sure whether these fixes have made it into a released snapshot yet.
It's quite reliable on SSD and is able to fully rebuild the kernel+userland.
In answer to your questions:
sdcard access from OpenBSD (either internal or external) isn't working yet unfortunately. I haven't figured out why, but it's probably a GPIO thing again.
To get OpenBSD working, you could download bsd.rd.IMX.umg to /boot on the internal sdcard or boot via TFTP. Attach either a SSD or a USB stick to install too and run the commands I originally posted to load and run the installer kernel. You should be able to complete an install to SSD or a USB drive at present (assuming the I.MX ethernet fixes are in the snapshot otherwise it will be slow and flaky).
If you install to SSD then you can create a small FAT filesystem and you'll be able to load u-bootified kernels directly off it. If you install to a USB stick, you'll have to mule the kernels back to the internal sdcard's /boot via Linux until one of us gets the sdcard support unbroken.
As far as helping with porting, there's still heaps to do:
i2c is flaky and is needed to get to the eeprom with display config to write a wsdisplay driver to get the screen working (only three steps in this yak shave). There's a small AX25 EEPROM driver in bitrig that could be modified for the 2nd step. Bitrig also has a better I2C driver, but I didn't manage to get it working reliably.
The sdcard and AX ethernet problems need to be figured out.
There are quite a few I2C drivers that could be written, e.g. for the MEMS gyro/accellerometer and various other things.
PCIe needs to be got working
A lot of problems would be easier if OpenBSD had good FDT support...
Longer-term goals: SMP, FPGA kernel driver, X11