They actually look very healthy. They need much taller supports, however. You can just use twiggy branches. Maybe some prunings from those shrubs beyond the window?

As to putting them outdoors I can't help you because I don't know what your temperatures are be like. But they do look rather advanced for hardening off successfully.

Rather advanced for hardening off successfully meaning they are too big now to do it (should have done it earlier)? Or that they are a good size for hardening off?

I know they need taller supports but figure I need to plant them in a big pot to do so, right?

Temperatures right now are highs 52-57 with lows 39-45, raining or partly cloudy or overcast.

Meaning that they are a bit too big. They harden better when they are smaller. Not saying it can't be done but there's a lot of soft grow there to be whipped about and bashed by the outdoor weather, not to mention whatever the temperature might be. If they've been inside they have been kept warm and have also had no physical pressures to toughen them up.

Regarding the pot size you could put them in larger containers but to be honest, as long as you feed them I think they could well manage in the pots they have, rather than stress them by transplanting when they are so far along. It rather depends on the variety. They could be anything from 2 - 6 feet tall at maturity.

I just worry that since they are from a bag in Trader Joes which is probably commercial farming that they will turn out to be 5 or 6 foot plants and they aren't going to make it in these pots that are only several INCHES across and deep (E.g 6 inches by 6 inches and that middle one is even smaller!)

I was thinking of taking all 3 pots and planting those plants into a large one where I could set up a good trellis system. Even if I kept it indoors. Is it likely that the plants will/can flower and produce pods at indoor temperatures?

Should I just keep them indoors and keep that room colder/no heating?

Also what kind of feeding should they get going forward? I planted them with a bit of slow release fertilizer beads but not much because I heard too much nitrogen can be an issue.

Zone 9B is definitely warm enough for peas to survive outdoors. They can take a little frost. What they have problems with is being waterlogged and wind damage, because the plants are brittle. This is where they need protection. Slugs also, but your plants are almost too tall for slugs.

Height is an issue, but your mother will know whether they are a 6ft tall pea or a 2ft pea. If they are short, then just like floral suggested, stick some shrubby prunings in, rather than single smooth sticks. Shrubby prunings with lots of little twigs also give protection from wind and the pea's tendrils can find something to cling on to.

Hardening them off is a good plan. Whilst I am not familiar with your climate, if you are zone 9b, then late autumn starting may not be such a bad idea. For example, the Swiss variety 'Winterkefe' is named 'winter', because these are traditionally sown during October and overwintered outside with a cover to prevent damage from heavy snows. Presumably in zone 9b you don't get layers of snow. These peas might stand a reasonable chance in free-draining soil and with some wind protection. I wish you good luck with them..

Thought I would give you a final update and thank you for your help.

I replanted the peas in a giant pot indoors and ultimately got a small crop full of peas out of my plants! And finished everything off with a pea shoot salad with lemon and shaved Parmesan.

It was definitely tricky growing peas indoors during winter and I wouldn't recommend it, but it was very rewarding to take some store-bought peas and turn them into another crop.

Thank you!