Many people (not all) experience a fall “lash shed” in which they shed more lashes than normal and the overall lash line appears a bit thin as a result. If this continues for more than a few weeks (4ish), it might be something else, but for now I wouldn’t worry. Try not to rub your eyes too much in the meantime. They’ll grow back to normal fullness.
As for using oil-based remover, I have never personally noticed it causing an issue with tint removal but it’s entirely possible. When I was tinting or getting extensions regularly, I used a gel-based remover by Borboleta that was specifically formulated for use with either. I believe they now sell directly to consumers, but your lash tech should also know about it. I actually continue to use that remover because I hate dealing with the oil.