Sorry, I accidentally deleted my earlier post when I tried to edit it.
The dark biplane looks like a Brunner-Winkle Bird with a much larger Wright engine. The paint looks like it's from the 60's or 70's, like the age of your photos. I believe it could be NC914V, which still has the larger engine and I can find photos from that side showing a match on the cowling details. The newer paint scheme is different though.
The other 2 biplanes are already identified so I won't say anything about those.
I still think the Seversky is the AT-12 Guardsman, which was made for export to Sweden. Only 2 of those 50 or so ordered made it there and the rest were impounded in 1940 and sent to US AAC bases. This AT-12 ended up at Lowery Field in CO and was restored at the Planes of Fame Museum in Chino CA. It's still airworthy I believe. I also believe there were some cowing changes over the years, mainly covering up the nose gun ports. I found a recent inflight photo showing the ports covered.
There are 3 P-35 survivors that I can find. One is restored and is in a museum in Sweden. One was in Sweden and was shipped to the US in 1971, it ended up at the Weeks Museum in FL, and is being restored. The third was in an aviation maintenance school in MN and then was bought by Chuck Doyle, a well known pilot in MN. I don't believe it was ever flyable after the war. It was restored and traded to the USAF in about '69 or so, and now sits in the NMUSAF in Dayton OH.
I wish I could post a photo but I don't think SC.org will let my because I'm not a paying member.