If the packages were in the image you flashed, you can't "delete" them and gain back flash space. "Delete" for firmware just means that it is made inaccessible.
If you added them afterwards using opkg, then yes, you can actually delete them.
If you can't get the device to respond to ssh (which hopefully is running even if LuCI can't), then failsafe mode would be the next step.
You should also be aware that "4/32" devices are unlikely to be able to run LuCI, or OpenWRT in more than a very basic configuration. If you want to try OpenWRT without LuCI, I'd suggest trying a snapshot.