Is there any emails for some black and white or it's just phone calls all the way throughout the entire process?

Just phone call. They just said the recruitment process has started.

At certain important milestones of your application process there will be emails. Eg, verbal offer, certain important clearance forms, POC. The other details are usually communicated through their workphone.

Any idea what is the salary band for Assistant director in MINDEF?

Hi, try to get shortlisted first, pass through the 1st round interview first. You can directly ask the HR and save yourself from all the false information here. The salary depends on ur DX rank. The position name , asst mgr, mgr, director doesnt mean much.

At which DX rank would you say it's worth it?

DX11, Snr Mgr i feel is the most value for money. theres alot of jobs currently that does more than some DX11 but only have estabs up to only DX10. perhaps due to poor planning previously.

between high 6k to low 10k roughly.

they offered me DX9

how about for fresh grad?