It doesn't sound as thou it's a load bearing wall, but to be safe in removing 17' of supporting wall, I would go to a reputable lumber yard and talk to someone about a engineer lament beam, they have access to the information and will give you what your looking for. They aren't cheap but once it's in place you can forget about it. I just recently built and used several the longest spans 25' and it T- bones into another one that's 20' mid-ways and their as straight as the day they where installed. I'm thinking their ran around $3 - 500 each. Sounds pricey until you see no sag in a room that's 20'x45' of nothing but open air.
I'm not a professional., But I did stay at Holiday Inn Express last night.
Gun control isn't about guns, IT'S ABOUT CONTROL.