If I had this setup I wouldn't bother with a tyvek or thin denier floor, especially with a big dog's claws. Instead I'd configure a poly tarp cut to size with whatever doodads you want to use to keep it in place. A 10mil poly tarp works great for keeping wet ground or snow melt from sponging up with your body weight---and if it's white you can see everything on the floor.
Example inside my tent as a second floor---
P1000218-XL.jpg
10 mil is thick enough to turn away small thorns---and this kind of "walmart" tarp is disposable and cheap and easy to cut---and dang waterproof. 10mil is beefier than the usual "blue tarps" and heck you could really get beefy with 12mil or 16mil.