A PoE injector is a worthy (and relatively cheap) investment for a basic diagnostic tool. That'll at least allow you to power up the cameras and tie them into your network where you can hopefully find them (the Fing app for iOS/Android is extremely helpful in this manner). Not to mention saving you a trip up the ladder.
1080p is the bare minimum for an IP camera anymore. There's absolutely no reason to drop lower. In the case of Hikvision, some people drop their 3 and 4MP cams down to 1080p for the improved night vision. I have found it to be tolerable enough that I can live with some grain in order to gain a full 4MP image. (none of mine are setup as very far range cams, so the close range helps offset less image quality at night). It ultimately depends on the scene in question. My front door? Absolutely no way I will drop that below 4MP. I get way too many expensive packages (without signature unfortunately) to have one walk. It has never once been an issue at all, but I don't want to cut corners. Right now the porch cam serves mostly as a pre-screening measure as to whether or not I'm going to answer the door. UPS/FedEx/DHL/USPS? Absolutely. They're my santa claus. (I regularly get presents each week, yay!) AT&T U-Verse solicitors, Jehovah's witnesses, etc., get rejected without being rejected. So much that I have that porch camera as a specific channel on my Living Room TV. it's 1 button press to quickly look, "nope not getting off the couch" or "yay Santa's here!"
I personally am a Hikvision fan, solely because of the hardware. It's been so very reliable and good to me, I haven't really had a need to venture elsewhere. Firmware is another issue that's a sour spot to me and many others, but I've learned how to coax it into behaving (mostly) the way I want it to or the way it's supposed to.
I would also like to point out, if I didn't already, that it was an absolute miracle you got the response and support that you did from a company that's seemingly non-existent. That is a very impressive feat for anyone in today's world of ever-worsening customer service, especially with these very thin Chinese firms cranking out cheap hardware. From what you described he seemed willing and informative and walked you through a ton of steps to try and bring it back to life. Sadly there are some US firms that wouldn't live up to that. Kudos to whomever it was you spoke/emailed with. Far and few between...and congrats on getting as far as you did! I wouldn't have had the patience. Even if in the end you end up replacing it, it was worth the trouble because you learned a ton, both from him helping you and on here. Can't get the pleasure without the pain.