Allow fingerprint unlock but require password after a certain time limit
Samsung has its own ways of implementation so this may differ but stock implementation :

Fingerprint can unlock the phone after it goes to sleep ( Settings &radar; Display &rarr;  after xx minutes of inactivity) only if Power button is not used to lock and default lock screen is used

If you enable power button locking or any third party screen lock / launcher that can lock screen, you can't unlock with fingerprint. You require to enter PIN

That is a far more easier way of achieving what you want (though you can't configure the delay) going by the need in your example

If you really need a configurable interval, that may be possible but would surely need root