Transfer of US assets to Japanese brokerage

Hello,

I am a current US resident that is planning to move back to Japan soon. I am a Japanese citizen, fluent in Japanese. Just unfamiliar with the Japanese side of things since I haven't lived there since I was little.

The one thing I'm a bit nervous about in regards to my move is transferring all of my ETFs/stocks. It is in the 7 figures USD.

What I've done:

– I created an IBKR-US account earlier this year and transferred all assets there (easy)
– I checked with IBKR and they mentioned once I'm in Japan, to notify them and they will transfer assets to an IBSJ account for free
– I have made sure that the ETFs/stocks I own are handled by IBSJ (i.e. listed under 取り扱い銘柄一覧 on the IBSJ site), as well as double-checked this directly with IBSJ

Now my questions are:

1. If anyone has gone through this process, how long did it take? If it happens too slowly, do I need to worry about my assets being stuck in IBKR-US? Assume this move is permanent, where I'll give up US residency completely.
2. Do I need to first open an account in IBSJ, or simply notify IBKR-US that I'm in Japan once I move and they'll automatically do the account creation on the IBSJ side? If I have to create an account, any one have real estimates on how long it'll take to stand one up, post- 住民票登録＋マイナンバーの付与?
3. Are there other brokerage options others have used that'll do an in-kind transfer of US assets from a US brokerage? I assume there aren't many from when I researched. For example, SBI mentions 外国証券の移転, but it has to be from another domestic brokerage. ("海外の証券業者からの移管申込は、受付できません。")
4. What is the customer service for IBSJ like? Particularly in Japanese, not English (assuming English service will always be equally good at best and subpar otherwise).