Well, the 'Paths' that I had a really clear idea for were Magic and Melee, and the rest were made for more options, so they didn't have quite the same germ of creativity behind them. I personally thought Defense was the least formidable, but it hasn't seen a lot of criticism. Stealth isn't exactly about making the Guadian Angel stealthy, it's about making her a better supporter of a stealthy ally. I kind of wanted her to gain the ability to be summoned at a distance to provide flanking bonuses (or appear on the other side of a pit, or outside of a jail cell) and then I couldn't find much flavor-wise besides more sneak attack and the Sacred Strike feat.
The Ranged path obviously suffered from a lack of inspiration as well. The first ability is essentially Precise Shot, BUT it's meant to only work when bonded allies shoot into each others' melee or the Guardian Angel's, so by the time you've spent text explaining that, you don't save any wordage by mentioning Precise Shot (also, Precise Shot has no bearing on shooting into a grapple, but I couldn't find the rules for that). The second ability comes at level 11, not level 7, and the third ability, well, I just didn't want to list every possible feat that could be on that list and I hope that people don't need rules lawyering and could just use common sense.
As for the magic path's third ability, I don't know what you mean by "individual spell level" vs "highest spell level channeled." But, it comes at level 19, so the wizard in the party is doing insanely scary things, and the stuff that a 9th level spell does makes the Guardian Angel gaining +9d6 damage in the process almost irrelevant.
Vengeance is less exploitable than you think. You specifically cannot do what you described, as spiders and rats are not animals. I may change it in the following ways, though. 1: The Guardian Angel has an alignment restriction of good, but I haven't yet made rules for what happens if they break it, so intentionally sacrificing your pets or allies could result in a loss of class abilities. 2: Make it take a week to bond with an animal (the normal time to teach an animal a trick). 3: Significantly reduce the number of bonded allies so that forming a frivolous bond like this is less attractive. 4: Give the Guardian Angel morale penalties from grieving afterwards (once the initial fit of vengeance is over).
I will consider where clarification is needed on your other points. Thank you for your PEACH.