First, we'll get your conditional value list working and then I have a comment/question on why you have separate tables for deficiency types and their descriptions...
You need a different relationship in order for your conditional value list to work.
Deficiencies::SectionID = DeficiencyTypesBySection::SectionID
DeficiencyTypesBySection would be a new occurrence of DeficiencyTypes createc by selecting it and then clicking the button with two green plus signs. Deficiencies::SectionID should be formatted with a value list where Sections::SectionID lists values in field 1 and Sections::SectionName lists values in field 2. This way, the user can select a section by name, but the value list enters the ID you need for your value list.
Now format Deficiencies::DeficiencyTypeID as a value list listing values from DeficiencyTypesBySection::DeficiencyTypeID in field 1 and DeficiencyTypesBySection::Description in Field 2. Select the Include only related values starting from "Deficiencies" option to limit your list to the specified section.
Now about that Descriptions table: You have set up a relaitonship for many descriptions for one deficiency type yet your example screen shots only allow for the display of a single description. Do you really need this table or will the Description field in t the DeficiencyTypes table suffice? If you need to display multiple descriptions, you'll need a portal for this on your layout.