Unfortunately it appears you "skipped " a step in the sanding process, ie you should have sanded again [ 80 and 100 grit] after applying filler, then applied stain.
Staining wood, especially pine, needs to be done by by book. Only remedy is sand off, buff with 120/150 grit and re apply stain
That pattern is called Chevron,it would have been laid in its raw state and finished on site[ most probably] Grade is rustic, knots allowed.
Its probably a matt oil finish .I am note sure if I am allowed to put prices here so if you wish to email me on firstname.lastname@example.org we can discuss further.
Each block measures approx 450 long x 140/150 wide
It would be custom made for you so you may choose your own block size.
I'm currently researching wood floors for a client. I came across this company that you might like to have a look at too. I haven't contacted them as yet so can't personally recommend. The Natural Wood Flooring Company