I've never noticed the chain reorg during custom json processing
Chain reorgs on Steem are usually rare, and usually only one or two blocks (so resolved within seconds), so you may not see them much. But sometimes they do still happen and sometimes take much longer to resolve, so you need some strategy for handling it.
If your app expects the user to retry or accept lost transactions occasionally, that may be a perfectly acceptable strategy.
Yes it is. Everything works as expected.