Very nice pond! Almost like mine back in my early days until my koi grew up and destroyed every plant in their path lol then I went full on koi-focused pond, no plants.

Here's some feedback on your list, don't take it personal, just my experience and the fact that you only get one shot at doing this.

Skimmer is garbage, it's filmsy. Basket design is prone to clogs. Stick with Savio if the funds allow or Atlantic water gardens: https://www.amazon.com/Atlantic-Water-Gardens-Skimmer-6-Inch/dp/B0056A7WLY/ref=sr_1_44?dchild=1&keywords=pond+skimmer&qid=1584141521&s=lawn-garden&sr=1-44

I would avoid the Tsurumi, it's expensive and an energy hog. If you can find a way to hide from the elements, external pumps are the way to go. But if you already own it, this could be a later upgrade.

That Rhino BD you linked is tough to maintain since the body is the width of your pipe. I went with a Koi Toilet as the base is much wider to get a pond vacuum in there.

Double liner is a no-go for full bottom drain setups, it will work for a retro bottom drain. Issue is it can interfere with the seal of the bottom-most liner and a leak there will be trouble trouble. I'd just go one single new liner if the old one isn't large enough. Also make sure to do a concrete collar for the bottom drain in case your substrate is prone to shifting.

Now is also a good time to get rid of all the rock on the bottom, you'll never look back after a bottom drain and proper filtration.

Feel free to reach out if you need more help/tips, I'd be glad to help.