To answer your first question about feeding while out, if you make your own baby food, then put it in a little container and wrap in tinfoil (keeps the cold in longer). Then use one of those little lunch packs that you can put an ice pack in. They make them with a little compartment just for the ice pack. Then you are good to go. 4-5 hours at room temperature while you are out is fine. Don't leave it in a hot car or anything. When we go out, I'll usually make up her lunch and do the tinfoil thing. Then I throw a bottle in there just in case too also wrapped in tinfoil. Heating them up, you can either feed cold or just get a cup of hot water wherever you are at and set the container in it for a few minutes. Or the bottle.
As for the eating dinner with the family, the only way I see that happening with you guys is if you switch your meal times closer to 6pm, and push the baby's closer to 6pm. You don't want to have her eating at 7pm, but your family might not want to eat earlier. If that's the case it's OK, your family will just have to accept that for a while you all aren't going to be eating dinner together.
As for the salt issue, I would refrain from adding additional salt to homemade foods for as long as possible. However, if you are cooking for the entire family, you can't make your food so bland that you all hate it. But you can add as little as possible and let everyone add salt afterwards to match their own tastes. That way you can offer her table foods now and see what she likes and doesn't like. Just make sure they are very well mashed up. And also make sure you know exactly what is in the table foods, because you will want to know if she develops a reaction, what is causing it.