Per policy session cap on Juniper SRX

Hello everyone!

I have a Juniper SRX firewall and in recent times I did had issues because
one or other user doing an attack outside. Usually it is compromised client
machines which create a lot of firewall sessions in outside direction.

I was thinking of two specific things as fix for this:

   1. Can I somehow put a cap per security policy so that all available
   sessions aren't chewed by clients?

   2. We have very few clients who actually use firewall in outbound, rest
   all in inbound. This I wish to skip firewall in outbound but in my test I
   found it behaves strange. I tried with machine having inbound traffic via
   firewall. They ping and port 80 also worked but SSH just hung up as soon as
   I started. I see SRX can be used in unidirectional setup but somehow it
   fails in my case.

Any suggestions/advice/ sample configs?

Thanks in advance!