I'm not even sure what "hotboot" is. There's a "fastboot reboot", but that's all. TBH if a full shutdown with battery removed doesn't fix it I don't think any form of restart will.
"fastboot flash boot C:\..recovery.img" sounds wrong to me. "fastboot flash xxxx yyy.img" means "reflash the xxxx partition with the yyy.img image file. "recovery.img" would imply a recovery image (like your 4Ext), but "boot" is the system boot partition, not the recovery partition. Flashing a recovery image to the boot partition would guarantee that the phone couldn't boot - whether it did other damage would depend on the size of the recovery image and the boot partition (if the recovery was bigger than the kernel - the thing that actually lives in the boot partition - then it would overwrite whichever partition came next in the storage. Nothing good would come of that).
The trouble is that I think you've tried most of the things I'd suggest: wipe cache and dalvik is the first thing, and if that doesn't work try using 4Ext to reflash the ROM. If it still doesn't work after that then I'm afraid that what's left is a factory reset (in which case texts etc are gone) or reflashing the phone with an RUU (which will return it to stock, remove root, remove 4Ext, remove your custom ROM). For that last option make sure it's the same software you had before rooting in the first place, since as I think I've discussed before some RUUs close off some options for re-rooting.
I'm not completely sure what is wrong here. Clearly your bootloader and recovery are still working. If the ROM had been damaged I'd have thought that reloading it would fix that. So unless we're looking at a hardware problem (in which case no software solution will help) that really seems to suggest some data corruption that is preventing it from booting, and with cache and dalvik wiped that only leaves a factory reset (unless this ROM is one that requires the kernel, i.e. boot.img, to be flashed separately, or you have already tried fastboot flash boot? I don't recall Desire ROMs needing a separate kernel flash, that was a feature of the 2012 phones, but just trying to make sure here). And if none of that works, then you appear to have done everything which only leaves reflashing the whole device as a last shot. I know that I'm basically repeating myself in this paragraph, but what I'm doing is showing you the thought process behind what I've written previously.
Perhaps now would be a good time to consider using 4Ext to make a backup of the phone - you won't be able to simply restore it, but it might be possible to recover information from the backup if you have one. Or boot into 4Ext, start the adb_daemon (USB debugging) and use ADB to copy data to a computer (even try adb backup, see whether that works). I don't guarantee that any of that stuff will allow you to rescue your data, but it may be worth a go to give yourself a chance of doing so.
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