Patur
1.First of all we Do say safek deoraysa by a safek esrog. the biur halacha that discusses rov is only to be somech on the rov to make a bracha. however, the bikurei yaakov holds that we don’t say rov there and still he holds you take without a bracha. There is no tzad in all the achronim there not to take an esrog. This is pashut just like by tefillin not one of the achronim (published) argue .
2. Ok so you agree according to sbeph and Rsm and RMS there is no excuse not to wear techeiles. Good. After a year and a half we finally got somewhere. And you agree that if there is only one safek of techeiles we all must wear it. Good. So explain what falls into the geder of a safek.
See the Chazon ish in Maseh ish http://hebrewbooks.org/pdfpager.aspx?req=51554&st=&pgnum=132&hilite= which clearly says we say safek deoraysa lchumra by techeiles just he felt the radziner was not even a ?? ??? of a safek. Today kyedua it was upshlugged that it lkulei alma is not a safek and the only people who wear it is only because they are chassidim.
I personally do not either see the janthina a safek as rav herzog only suggested it because of problems he had with the murex, which we now know are clearly not problems. Also you will have a hard time answering it up with most chazal and there is no raya to a janthina rather a hashara in which the yeshuas malco 2 writes
??? ????? ???? ???? ?? ??????, ?? ???? ???? ?????? ?????? ?????? ??? ???? ???? ??? ???? ?????, ???? ????? ????? ???? ?????”? ????? ?????? ????????? ??? ??????, ?? ???? ???? ??.
see also rav tavgar http://www.tekhelet.com/pdf/kuntreis2008_2.pdf
Now Rav Chaim only knew of one type of techeiles and RSM is also only talking about the Murex as the only candidate. so they have no excuse (Lulei the chazon ish which won’t help today)
3- I like the additional raya you brought from tekious against the way the velt says rav chaim.
4- you can wear all three sefeikos at the same time. I already pointed out you can make a tnai. Therefore you can be mesakein since you have done everything possible to bem ekyam the mitzva.