First, check if your hardware is still OK by loading a fresh Armbian installation from a new SD card.
Second, to trade off reliability over performance, it's a good idea to use "sync" instead of "data=writeback,commit=600" options for mounting rootfs - this should help preventing filesystem corruption in case of unclean shutdown. Also you will need to remove "journal_data_writeback" from default rootfs mounting options with tune2fs.
Third, for UPS, define "very expensive". There are 12v UPS devices like this, combined with lead-acid battery and 12v-5v step-down converter it will give you enough uptime to survive even long power losses.
Another thing - it may be a good idea to enable HW watchdog, but I didn't test how well does it work (if it even works at all) in legacy kernel for H3.
