I have a feeling 1sat /vb might be a thing of the past. Correct me if Im wrong.
You're wrong. 
It make take a few days or a few weeks, but the mempool will empty out again.What would you consider congested? I'm guessing if its purging transactions >300mb - its congested. Is that a good indicator?
I wouldn't necessarily say it was only congested if we start purging transactions. If we have been stuck with 200mb of mempool memory usage for a day or more, then I would definitely call that congested, for example.Also, checkout the total no. of unconfirmed tx chart in the mempool here: https://www.blockchain.com/explorer/charts/mempool-count
I don't find total transaction count a very useful indicator at all. We can have thousands of transactions which are only a few hundred vbytes in size each and don't take up much space at all, and conversely, occasionally an exchange like Binance will drop a handful of consolidation transactions which are all tens of thousands of vbytes in size. We can end up with the same amount of block space taken up by 10 transactions or 1,000 transactions.Personally, I use a combination of https://mempool.space/ and https://jochen-hoenicke.de/queue/#BTC%20(default%20mempool),8h,weight to pick my fee for a transaction.