If I am at full retirement age (66.5 yrs old), and first take spousal benefits on my husband's record, can I still receive the 8% annual deferral credits at 70 years old on my record?
Potentially yes, but only if you were born prior to January 2 1954. This is due to amendments in the deeming rules passed by Congress in 2015 (https://www.ssa.gov/planners/retire/deemedfaq.html).
Full retirement age (FRA) for people born prior to January 2 1954 is age 66, so if your FRA is 66.5, I assume you were born after 1954. And, if that's the case, the answer to your question would be no. You may want to consider running the maximization software available on this website in order to explore your options.