Wow congrats.... Yah, if you can do so now, you should. Singapore is too stressful... work and work.
My personal opinion is you should sell your SG terrace while you can, since you've already had it planned out. If you have read numerous reports, there is also oversupply of properties in Singapore for many years. Prices will continue to drop along the way. But just my advice. I may be wrong.
If you foresee going back to SG now and then, you definitely need a car to be parked in SG right? So you'll have 2 cars, one in SG, one in Johor.
I didn't know you can rent a Johor 4 bedroom condo, 2000 sq ft for only RM1600?!! That's dirt cheap! Do you mind sharing roughly which area this is? Thanks.
Over supply in Singapore but not for landed, keep as heirloom is my advice, unless in real dire straits.