When we ran 90T1-B3, but on a 4" plate, we did a N&T with the temper being 1300F for 22 hours, and the tensile tests came out at 80-81 ksi. The chem was .09C, .71Mn, 2.47Cr, and 1.05Mo. I am really surprised your 90S-B3 test came out so low, as your tempering temperature is a lot lower than normal for this kind of alloy. Also, what kind of gas are you using? If you are using 75/25, switching to something like 98/2 might increase the tensile strength enough to put you over the top. If you have to stay with GMAW, you might look at ER100S-1 (we passed a 90ksi min N&T with SMAW 10018M and a 1190 temper) or a metal cored wire. There is more flexibility in getting a metal cored wire than solid wire and you might be able to find one that suits your needs more closely. Unfortunately, N&T applications are out of the norm, so I haven't found manufacturers to be able to offer much help with these kind of issues either. Also, what kind of tensile specimens are you using? I have found that .505 diameter specimens are not the best when your tensile strength is close. You might try as large of rectangular specimens that you can get pulled, and the tensile usually goes up a few KSI. It also is a more realistic test than the little round tensiles, so it's not even really "cheating".