Income information in non-ASEC samples is sparse. EARNWEEK and HOURWAGE are part of the Outgoing Rotation Group/Earner Study, which means only respondents in sample months 4 or 8 are eligible to respond. This is why you are seeing a large number of NIUs.
Since CPS respondents are in the sample for 4 months, leave for 8 months, and then re-enter for a final 4 months, some respondents will also appear in the ASEC. You can match respondents between these basic monthly samples and the ASEC by using HRHHID and HRHHID2 to link households along with LINENO, SEX, and AGE to link respondents. Once linked, you can use the income variables available in the March ASEC.
Finally, as you mention, there is a categorical family income variable (hufaminc) available in the basic monthly samples; however, it is not currently available via IPUMS-CPS. See this previous answer for information on linking your IPUMS-CPS dataset to the source NBER data. If you choose to use hufaminc, it will be available for all respondents in your basic monthly samples.
Hope this helps.