Direct MYR to SGD coversion will only work for lower level jobs <RM6000. If you are making more than that, you will have to moderate accordingly.

What exactly you mean by highest level in R&D engineer? It does not seem plausible that one can reach highest level in engineering in a US MNC at your age. Do you mean that it is the highest non-manager technical position?

Housing allowance, kids education, car allowance etc. are considered expatriate benefits usually only for Senior Managers, I don't think you will qualify. At most you can negotiate some sort of support allowance, you need to elaborate more on what level you are now so that I can estimate max. you can ask for.