Is there a way to show the number of open lots for a particular asset and algo?

I tried with LotsPool, but I found out that it only display the open lots for an assets, but it doesn't separate it based on algo. Other trade statistics doesn't seem to give this data.

Yes. For any given asset() and algo() combination, call for(current_trades) { ... } and add up the lots for each trade (TradeLots).
https://zorro-project.com/manual/en/fortrades.htm
https://zorro-project.com/manual/en/trade.htm