point 1 and 2 are not immune to 3, infact, they are pretty much the same exept you are storing the data differently - you need to have a place to store the blockchain, but it's not decentralized if there is only 1 node, but you have to start somewhere
so i don't see anything wrong with storing the data in a database, it's just not really a decentralized block chain without lots of nodes (i.e. a network each has a copy of the blockchain)