Ok, back to your initial problem: You can add extra filters to the Elasticsearch ingest pipeline. So if your input doesn't match the provided filters, you have to add extra ones (Remember, they are processed sequentially). Why your log doesn't match the pattern/filters is beyond my knowledge It can be that you have a custom log format on your ASA or that the provided filters in the beat are broken. Since both of us have problems with it, I guess there's a problem in the provided filters. We (meaning not you but the people who worked on our side) could work around it by introducing new filters into the pipeline.
I can just encourage you to open another thread about ILM with Logstash here if you haven't. It does work but it's not as easy to start with like Curator.