Is there a policy that states that if the Non-IT requirement is less than 51% service then it would be considered supply with incidental service?
The scope described in the question background of this question appears to be construction as the work is altering a building and will result in a "complete and usable improvement to an existing facility" IAW 10 U.S.C. § 2801. According to FAR part 2, construction is defined as construction, alteration, or repair on buildings, structures, or other real property.
The definition of a service contract is at FAR 37.101. A service is performing an identifiable task rather than to furnish an end item of supply. The definition of supply is in FAR part 2, which means buying property, all property except for land. Ultimately the contracting officer will have to make the determination of classifying this requirement as to the type of buy.