Thanks for your questions. I am the architect and engineer working on https://bridge.harmony.one/. There has been no security issues wrt bridged assets. We had a full audit done by PeckShield (Security Audit - Harmony) before the launch (oct 2020). Since the launch, 10+ months, we had no issues and the bridge has over $90+ million tvl. Will be happy to provide further details if required.
With regards to harmony network itself, 4 shards secured by 1000 validating nodes. 800 out of 1000 validating slots are run by the community. As per Harmony – Open Consensus for 10B, you can see 126 unique validators securing the network (with similar decentralization of each shard Harmony – Open Consensus for 10B). Overall, the network is secured by 4,615,419,443 staked ONE tokens, worth over $460+ million. Note that, harmony network has been up from Jun 2019 (with open staking from May 2020), had multiple audits with no security breach. Again, I will be very happy to provide further details and help you to evaluate.