I'm not the owner of that site. It's just useful and probably the best one to analyze the mempool.

I don't have any other good site.  https://tradeblock.com/bitcoin/ used to work but it is not completely reliable.

Transaction per second is not a good measure of mempool status because transactions differ in size a lot. It's probably best to take a snapshot of the size of the  mempool at time t, compare to t+dt and add the size of blocks mined at that time.