[RPG] What happens to a petrified familiar

Checking the rules for the petrified condition, Enlarge Person and for transmutation spells in general shows that there is nothing that mutually excludes both effects at once. Specifically, a petrified humanoid does not change type and become an "object" - it is still the creature, but with a condition applied.

There is no apparent "freezing" of ongoing effects, spell durations etc, which should really be noted under the condition if that was the case. There may even be undesirable exploits to make cheap permanent effects tied to petrified creatures under otherwise temporary effects.

So in my opinion, that supports your option 2:

(2) The petrification creates a statue of one's current form, but when the spell wears off the new stone statue changes shape.

However, I think there is ample room for DM interpretation supporting either of the other two options, and even variations depending on what kind of effects can be "frozen in" when a character is petrified. It would be a minor ruling either way, and only require a little consistency during the game.

A side-effect of supporting option 2, is that if you cast any visible effect that does not affect normal objects on apparent statues, then you will see which ones are in fact petrified creatures from how the spell works (or not). As there is no competing "detect petrification" spell as far as I know, I think that is probably ok.

It's just a temporary inconvenience, except in a singular case.

Basically, all that a familiar's death means is that you'll have to recast Find Familiar at your earliest convenience (so it means the loss of a spell slot for a day if you have a time pressure and can't take the extra 10 minutes to cast it as a ritual). The spell/ritual does cost 10gp, but that's a pretty trivial amount for an adventurer. It also has a casting time of 1 hr so your party probably needs a short rest while you do it rather than simply doing it between encounters.

The only case where having a familiar come to harm is a permanent issue is in the rare event that you decided to retrain the spell (or as a wizard, have lost the spell book that contains it). These are the only times when losing a familiar has long term ramifications.

As to whether or not the newfound familiar obtained when you recast the spell is the same being reincarnated/resurrected, or a different being entirely, this is up to you and the flavor you choose for your familiar.