With an 11/2 Mission coupling toque to 80 in pounds.
You need to check for a clogged pipe .
Washing machines pump out a large volume of water and todays standards require a 2 inch drain pipe. Bathtubs generally have a one and one half inch drain. So bathtub drain will have to be increased to 2", including trap and 18 to 24" standpipe to operate correctly, and connected to the closest existing 2" line or larger line. Same 11/2 venting can be used.
It's not the toilet, there's a blockage in the pipes some where after the drain pipe from the toilet joins up with the drain pipe from the tub.You're going to need to have the pipe snaked.
Probably the wrong size flange. Is the flange a toilet collar? If so the pipe is probably 4 inch.
1/4 inch per foot.
1-1/2 inch drain for above grade and 2 inch drain for below grade. Most UPC-based codes (IAPMO) require 2 inch above and below grade.
100
Well if you have another bathtub then use it because if the pipe has no water in it the orbeez will dry out and go into the sewer easily without blocking the drain
1/8" per foot.
a 3 inch pipe
yes
Put an adapter between them. You can't transform it, you can replace it or change it at some point to 2 inch and continue with 2 inch.