Of the top of my head, can you try to use the 'q' operator for the string literal
something like
insert all
into domo_queries values (q'[select
substr(to_char(max_data),1,4) as year,
substr(to_char(max_data),5,6) as month,
max_data
from dss_fin_user.acq_dashboard_src_load_success
where source = 'CHQ PeopleSoft FS']')
select * from dual;
Note that the single quotes of your predicate are not escaped, and the string sits between q'[...]'.