What version of Squid are you running? What release of linux?
I am running 2.6STABLE9 on CentOS 4.4 and had to compile squid with netfilter support and add transparent option to squid.conf.
The options you list above I thought were for BSD systems as I understand.
How is this setup working for you? I just recently switched from the integrated Mikrotik caches(tried both) to DST-NAT'ing to an external Squid. Works great overall. Websites that use a form of NTLM for authentication work fine with squid 2.6 where they did not with Mikrotik or 2.5 squid. Seems to run much faster too. CPU load on Mikrotik used to hit 100 percent at peak times when it was caching. Now that its just DST-NAT'ing to squid it peaks at 9 percent. Squid box peaks at 1.5 percent CPU load.
There is one problem. At certain times usually peak times certain IP's trying to use the cache will lose access. They can do everything but http. They can even ping the cache. At that same time other users will be using it fine. The stats on squid will look great and there are what looks like plenty of free 'file descriptors' according to squid stats. A few minutes later and that user will come back.
Not sure what is going on. Perhaps the Mikrotik DST-NAT table has all it can handle at 400+ IP's with a large number of connections each at peak times? This is on Mikrotik 2.9.39 release. Any ideas?