I got my undergraduate degree from Western in the mid-80’s and have watched dozens of games over the years. Thompson Arena opened in 1973 and at the time was a great multi-purpose facility. On entry, to the right was the rink, and to the left was 4 curling sheets (great entertainment during intermissions as there was a centre concourse with glass looking in on the curling). The portion of the building to the left, including the curling rink, was demolished about 12 years ago and made into a modern fitness facility for students, which today is still top notch.
The hockey arena portion of the building does indeed have a track around the rink. This is used for indoor track and field, with the ice covered for the field events. On the camera side of the stands is permanent seating for about 400, with portable bleachers at the lower level that extend out over the track. The camera side seats about 700-800. On the opposite (west) side of the camera are huge banks of retracted portable bleachers. In the 80s and 90s when the Stangs made the playoffs, these would be pulled out and mostly filled. They don’t seem to have anywhere near that following now and these seem to now only get pulled out for high school games. The area you mention, behind the net on the south side, is a bit of a beer garden (used to be portable seating there too). You do need a ticket to sit there.
When I attended capacity was listed at about 5100, but I think it’s under 4000 now. It is not a great atmosphere for watching a game, unless the west side bleachers are out and full. One of the reasons they moved their home games to the John Labatt Centre (now Budweiser Gardens) for a couple of seasons back around 2007.
