Very simple to solve this problem. The best thing is your husband support you. Let me explain:
Assumptions:
Your 99 has downpayment: 2M
Your old flat costs 3M, 650sq feet.
Your new flat costs 5M, 1000sq feet.
Situation 1 (Current situation)
Your have no name.
Live in new flat
Keep your 1M.
Pay 0.15M for decoration (I support this, you live in ma).
You husband need to pay mortgage 3M. (5M-2M from 99)
Situation 2
Repay your 99 2M.
You pay 1M.
Your have name, 99 has no name.
Live in smaller flat ($3M for 600 sq ft)
Any 0.15M for decoration? (Still have spare money?)
You husband need to pay mortgage 4M. (3M+2M to 99 - 1M from you)
*This is very stupid. Higher debt, poorer living standard.
Situation 3.
Your have no name.
Live in new flat
Keep your 1M for investment (say 5% return).
Pay 0.15M for decoration.
You husband need to pay mortgage 3M. (5M-2M from 99)
Ask your husband to buy a life insurance that pay you HK$3M if he dies (no saving, no investment). That should be cheap. If he is not here anymore, you can get $3M cash and his 50% share of the new flat. Since your 62, 99 is rich and you have a son. I don't think they will ask you to move out because you have 50% share (inherited from your husband).
This is the better situation because
1. You live in a bigger flat, better living standard immediately.
2. You can keep your 1M for investment.
3. You have protection from the insurance.
4. For your husband, the mortgage is 1M less than the situation 2. The saving is more than the insurance installment.
So, it it even better than situation 1 la.
Don't be upset. Just think your 99 is so kind to give your husband HK$2M interest free loan! Couples with poor 99 cannot get this support. You are lucky enough!
Discuss with your husband! I guess he will do what to make you feel happy! Cheer up!