Are there any ways to sync mempool from another nodes faster?
I had a similar issue where I restarted my bitcoin node for changing some parameters and it took half a day to catch upto to all uncomfirmed tx. Bitcoin 0.14 has a feature that stores current mempool to disk and loads it back on startup https://github.com/bitcoin/bitcoin/pull/8448. It should be possible to copy mempool.dat files to your other nodes that are behind.