1. We are going to need a picture, but why not mount the beam same way as before ? Just make sure the weight is sitting directly over the post --- not that the welds are taking the weight.
2. Check the wording on the code. I can understand needing to resist lateral loads, but there are ways to do it other than attaching to the house. If the steel posts are embedded in concrete, I would argue that resists lateral loads. I have an inspected free-standing deck that resists lateral loads by angle braces.