Favored Class Bonuses

You're correct on how the favored class bonuses would be distributed for the most part. Basically, you gain the bonuses at every level, and you can mix and match them, as long as you continue to level up in your favored class. Half-elves also get two favored classes, so if you ever multiclass, you can still gain favored class bonuses on your second class.

A few things though!

1) The Con Mod applies to every level up, so it'd be 5d10 + 5 hit points at level 5.

2) Also when I looked it up, the half-elf's favored class bonus for ranger was "+1 skill rank for their pet". Is the DR one in a miscellaneous supplement?

3) At level 4, the ranger chooses between bonding with their companions or gaining an animal companion, so you couldn't start taking any favored class bonuses that apply to your pet until you actually have a pet!

Whatever you do, I'd say take it earlier rather than later, since 1-2 HP matters more at low level than high level. Just my take.