I solved my problem with @Marc's help.
Here's what I did. Hopefully it will help someone else.

Read above to understand the challenge.
TL: DR; Use the 3rd segment in the URL as virtual/dynamic to serve any content node under a single docType-content-template.

Step 1: Register a content finder as described in the IContentFinder documentation. I skipped the "remove, append and insert" statements.

Step 2:
I created a folder in the root of the project. I named it "App_Code". Inside that folder I created a c# class (.cs file) named ProductContentFinder.cs.
"ProductContentFinder" is also what needs to go in the contentFinder composition, like so:

composition.ContentFinders().InsertBefore<ContentFinderByUrl, ProductContentFinder>();   

Step 3:

using Examine;  
using System.Collections.Generic;  
using System.Linq;
using Umbraco.Core;
using Umbraco.Core.Models.PublishedContent;
using Umbraco.Examine;
using Umbraco.Web.Routing;

namespace Myproject.App_Code
{
    public class ProductContentFinder : IContentFinder
    {
        public bool TryFindContent(PublishedRequest contentRequest)
        {
            var path = contentRequest.Uri.GetAbsolutePathDecoded();
            var pathSegments = contentRequest.Uri.Segments.Length;
            if(path.Contains("/products/automotive") && pathSegments > 3) // products is my landing page. automotive is my child page and only execute if the url has 3rd segment (the virtual one)
            {
                var virtualSegment = contentRequest.Uri.Segments.Last(); // this will used to find the desired virtual node
                if (ExamineManager.Instance.TryGetIndex("ExternalIndex", out var index)) // decided to use Examine to search for the virtual node
                { 
                    var productPublishedContent = new List<IPublishedContent>(); // just a container
                    var targetLandingPage = new List<IPublishedContent>(); // just a container
                    var productSearcher = index.GetSearcher(); // dedicated searcher for the product (virtual node)
                    var productResult = productSearcher.CreateQuery("content").NodeTypeAlias("productProfile").And().Field("urlName", virtualSegment).Execute(1); // run the query and limit to 1 item. "urlName will match the virtualSegment
                    if (productResult.Any())  // did we get anything?
                    { 
                        foreach(var result in productResult) // should loop only once because the query has a limit of 1
                        {
                            var productNode = contentRequest.UmbracoContext.Content.GetById(int.Parse(result.Id)); // returns the IPublishedContent node
                            productPublishedContent.Add(productNode); // add to the empty container. the container was declared outside the if and foreach for scope purposes
                            var landingPageSearcher = index.GetSearcher();  // dedicated searcher for the target landing page
                // given the structure on the content tree matches the structure of the catalog (see above), use the name of the parent node to find the target landng page
                            var landingPageResult = landingPageSearcher.CreateQuery("content").NodeTypeAlias("childPage").And().Field("nodeName", directoryNode.Parent.Name).Execute(1);
                            if (landingPageResult.Any()) // did we get anything?
                            {
                                foreach(var page in landingPageResult) // should loop only once because the query has a limit of 1
                                {
                                    var landingPage = contentRequest.UmbracoContext.Content.GetById(int.Parse(page.Id)); // returns the IPublishedContent node
                                    targetLandingPage.Add(landingPage); // add to the empty container. the container was declared outside the if and foreach for scope purposes
                                }
                            }
                        }
            // use the productPublishedContent class to merge the product node amd the parent node. This ensures that the virtual node is loaded as if it was an actual node that is part of the content tree
                        contentRequest.PublishedContent = new ProductPublishedContent(productPublishedContent[0], targetLandingPage[0]); // pass in the published nodes only. the containers are of List type
                    }
                }
            }
            else
            {
                return false;
            }
            return true;
        }
    }

    public class ProductPublishedContent : PublishedContentWrapped // inheriting from PublishedContentWrapped is what enables loading the virtual and parent nodes as one single PublishedContent object
    {
        private readonly IPublishedContent _productPublishedContent;
        private readonly IPublishedContent _targetLandingPage;

        public ProductPublishedContent(IPublishedContent productPublishedContent, IPublishedContent targetLandingPage) : base(productPublishedContent)
        {
            _productPublishedContent = productPublishedContent;
            _targetLandingPage = targetLandingPage;
        }

        public override IPublishedContent Parent
        {
            get { return _targetLandingPage; }
        }
        public override string Path
        {
            get
            {
                return _targetLandingPage.Path + "," + _productPublishedContent.Id;
            }
        }
    }
}

I'm sure there's a better way and perhaps more elegant way to accomplish this.
In the meantime. I'm just relieved that I got it to work.