Unfortunately this version of elasticsearch-shard doesn't correctly handle truncated translog files. This is fixed in #42744 but that's not released yet. The safest thing to do is to wait for the release of 7.3, but I can't tell you when that'll be. If you feel the need to try any other course of action, make sure that you can get the node back into exactly the state that it's in now, otherwise there may be no hope of recovery in the future.
If you had one node, in practice you will have had no replicas. Elasticsearch only allocates a single copy of each shard (either primary or replica) to each node, so if there's only one node it will only allocate the primaries.
Also this failure indicates that your storage system is not working correctly. A power outage alone doesn't cause this kind of corruption.