Well the simplest answer is to not filter it. If you let it clear in the fermenter, then transfer carefully so you don't disturb the sediment, you should have fine clear beer. A post-ferment clarifier like gelatin can be added to help any small particles fall out.
A week or two cold in the keg will help too. Any particles will sink to the bottom and get blown out in the first glass.
Sourness could be bacterial contamination. Make sure everything is well sanitized. What are you using for that?