how can i hack my husband cell phone?

Hack your husband's phone in 3 steps ...
1) get him drunk
2) hit him hard on the head just to make him unconscious(don't worry he won't feel any pain)
3) access his phone via his fingerprint or iris or face whteva security he's using to hide his stuffs from you.

All the Best!!

If you want to do that, you may as well file for a divorce. Clearly the trust isn't there.

Secretly video tape him entering his password.

Just no!