I grew some cuttings inside a grow enclosure, it helps hold in humidity; under constant artificial light, they grew very well.
Ichang papeda does have more drought tolerance than other citrus but in its native climate it still receives rain and is fairly humid during the summer.
For a small seedling growing outside, it's better to keep it consistently watered and put it in partial shade. (It still needs a fair amount of sun, but cooler morning sun is better) It depends of course on what your climate is like, but it should do just fine where you are, except for the winter.
You might even wish to cover it with a clear plastic bag (maybe with a few air holes in it) to help hold humidity. I don't think it needs that but it might help if you're in a dry hot area.
I don't think there's anything in particular about Ichang papeda that would make it more difficult to grow than other citrus.
It does tend to be a slower growing species, but I've found them to have strong dependable growth, they are not frail.
Make sure you're also giving the soil a chance to dry out just a little between waterings. You don't want the soil constantly wet all the time, that could contribute to root rot. But try to keep the soil from drying out too much for too long, if that makes sense.
I predict your seedling will survive and grow, as long as it's given a little water every 2 or 3 days, but because of its small size right now, it may be a while before it puts on much growth.
Edit: I did not see that it was grafted before. Now I'm thinking there's a possibility the upper part may be able to survive, but it's not going to do well any time soon.
Even cold hardy citrus like this does not handle sudden temperature changes from growing inside to being taken outside in the winter, so if you decide to try to grow it inside during the winter, make sure it does not go outside until temperatures have warmed up.
If it helps at all, my grow enclosure stays at about 78 F, and sometimes the temperature in there rises to 86 on hot days. With adequate humidity, they seem to like that.