Point 1, You have partially answered your own question, ASME IX has provision for several CuNi alloys as a P-34 material. Procedure qualification for pipe can be done on plate per QW-211
Point 2, If you are using D1.1 is intended as a code for carbon and low alloy steels. You can use it for CuNi, if the Engineer approves such use. (not sure why he/she would, but it can be done)
Figure 4.24(A) Performance and 4.25(A) Procedure in D1.1:2010 might be made to work with QW-463.2(d,e) Performance and/or QW-463.1(d,e) Procedure, in ASME IX:2010. It seems like a huge pain in the a$$ to do so, given the number of specimens, different essential variables, etc, etc. I think by the time you get done fooling around with it you could have run the 2 standard tests
FYI, for best answers on code questions, specification of the Edition year is important