Asked on 31 Aug 2020
Considerin buyin hdb resale after 35 under the singles scheme, then register the marriage (partner already has his name locked down in private ppty).
You need to complete the paperwork before your marriage. I don't expect HDB to be such a hooligan but you may want to check with them.
I was in a slightly similar situation (not about the singles scheme) but HDB assured me that they will not confiscate my BTO.
Until your husband sells off his private property + 30 months cooldown, you cannot apply for BTO as a couple. Since you are married by then, you also cannot apply for BTO as a single.
A quick look at HDB's website only says they do not offer grants to people who have higher income or own private property. Not sure what happens after your husband sells it off.