Regarding the Foam, I remove and use the bike only for ~10 days a month after that I am in need of FE so I will put in the foam again!
preferably 40T or 42T
43/14=3.07
42/14=3.00
40/14=2.86
Are you sure about the splendor stock rear sprocket (44T)? I remember it was 43T (I may be wrong) If current is 43T, I would suggest you to try 42T from Super Splendor / Joy. Anything beyond that will kill the low end.