bi-metalic corosion

?-on the plumbing manafold, out side the house, after the PRV, on the stub out where the Pressure valve should have been installed, is a plug, all rusted out. I believe the plumber simply installed a steel plug, rather than a brass one and now it has corroded the stub out and coroding the manafold. Could it have done additional damage in my house? How would I know? I recently had a water filter rupture and flood my kitchen, could the bi-metalic issue have caused additional corosion in the filter causing it to fail?

The rust may have plugged the filter, but not cause it to burst IMHO. If you can get it out and replaced, it should be fine, but you may have to replace the fitting as well depending on the amount of corrosion.