There is no best way, only ways that best accommodate you and your partner and later on your children.

>>Back to topic, anyone can give idea on how to give birth of baby in SG at a very low cost?
You can give birth in private hospital in Johor, it is relatively cheap compare to SG

You may also consider to buy house in Johor to bring your parents or your wife parents to stay in Johor and help look after your kids (assuming they are retired)

Or you can register your family as PR once your wife gave birth. It is easier to get PR if you apply as a family with your child

>>6. Don't have family in SG. Was planning to go back in retirement mode around ~45 y/o. Feasible?
It all depends on the lifestyle you want, and the things (education) you want to provide for your children. If you are able to gather around RM1 mil, you can have around RM5k per month just from interest. Not factoring in inflation

Children education is very important and as SG is a very competitive nation, children education also become very competitive.
If you are "competitive", there is way your money is burnt... numerous tuition and enrichment classes
The syllabus is usually more advance compare to Malaysia, get more exposure and they also emphasize alot of activities
Once your children enrolled in primary... secondary, it will be difficult for them to return to Malaysia, so if you plan to let your child study in SG, might as well convert to Singaporean to get the government benefits for his people

At one point or another you will have to make sacrifice.
Yes alot of Singaporean do retired in Malaysia (those that can drive and do not mind risking), but generally most elder Singaporean just stay in SG. Just check the kopitiam, park and town hall and you can see retiree enjoying themselves.
The question is what kind of life style you prefer, kampung life style, city life style?

For your reference, I travel daily between MY and SG. Move my whole family to Johor.
Children study in MY government school

It's damn tiring. But this is the price you pay to enjoy SGD1 = RM3 and having your family close to you.

I joined a car pool, drop me at mrt station in singapore and pick up from some gathering point near my my house.
Can take rest in the car.

I'm not expert in trading and investment... maybe you can get more information in the investment thread.
I think public security in JB is normal besides, you are a Malaysian right... JB is just like any other city in Malaysia... you need to be careful with your belonging and surrounding, that's all. If you compare to SG then yes, security level is different, but as Malaysia, you should do fine, we already heighten our senses
As for staying, just stay in gated and guarded area.

Lobang for car pool
Not lobang actually, it is huge business. Just google and you can get. All major township have such service but Bukit Indah area flourish the most.
You can even start your own business if you have a seven seater or a starex MPV


新柔快车Carpool JB-SG Public Group | Facebook
https://www.facebook.com/groups/Carpool.JBSG/

新柔快车Carpool JB-SG has 16233 members. The most fast and convenient carpool~~~. Support Group.
JB Carpool to SG Public Group | Facebook
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JB Carpool to SG has 7437 members. Welcome any member can add and approve new members.

Hmm... you can say save money but you still waste a log of time on the car. Minimum 4 hours per day and easily 6 hours if have jams.
6 hour in a car with nothing much to do except sleep and playing with phone.
Besides as these are car pool, your need to have fix work time means no OT. You cannot really cheong for your work.

Ya, use to be very popular last time, but recently after SG increase school fees for PR and foreign students, and also the launching of more new international school. There is less students traveling over to study