sbeph- go ahaid make fun of lamdanim when you can’t understand a gemara. the case in rh is talking about a safek deoraysa being mechayeva halicha to a makom that is a safek mitzvah even at the cost of being mevatel a derabanan. get it ? It is a safek if there is a mitzvah in the first place. Not a safek that you are mesakein like the ran. just are you mechayev to do a maaseh because of Safek doraysa that is not mesaken whachout , MR> sbeph you might embarrass yourself…..
Ain hachi nami the ran is different however being that rav moshe shternbuch ( in chelek 4)throws in the pri megadim 194,3 the ran disagrees with the pri megadim ( as well as the machatis hashekel shulchan aruch harav mishna berurah aruch ahshulchan the levushei serad and the pri megaim himself in countless other places ( like the end of siman 39). If you want the pri megadim then you have the ran ( which is paskened lehalcha by the mb)
And yes the Mb and everyone else disagrees ( like the biur hagra in 32 5 and many achronim spread out in hilchos tefilin)
And when I say i dont know where rav chaim comes from teshuvas vhanhagos won’t help. He does not either know where it is from. In chelek one he says the bais haleivi and in chelek 4 he says the maharil diskin ( he also adds how the radzhiner brings it down mishmo in his sefer)
about 20 esrogim – you are right and even patur will say no safek lchumra there.