I managed to get a $0.02 fee transaction (2.2 sat/B) confirmed after 88 hours (3.6 days).

Moreover, I put the dust to recipient at 1000 satoshis ($0.04)

(This cost will soon be $0.00 with the next update since the recipient address will be included in the op-return message)

See transaction here:

https://blockchain.info/tx/8701493a5eaaaf2a0a082e42c6693743d1e02bd43b61b0d917a52ae55c7001b4

https://xchain.io/tx/8701493a5eaaaf2a0a082e42c6693743d1e02bd43b61b0d917a52ae55c7001b4

The clue is that whenever mempool clears, miners include transactions almost no matter how low the fee is. After all, it’s in the individual miner’s self interest to include a tx and claim the fee rather than leave it for the next block’s miner.

When does mempool clear? Look at previous 10-20 blocks. Are a few of these less than 1MB? Then it’s likely the mempool is clearing and you can expect to be included in the next <1MB block.

If all recent blocks are full, expect to wait a long time. Mempool tends to clear when tx throughput is low (e.g weekends) combined with a lucky streak (sometimes lots of blocks are discovered within a short timespan).