Multiple Case studies, Canonical link to main service page?

[DaveAngel]

I have a client with 1 main service and approx 50 case studies (and growing) all with keywords relating to that service. Looks like I have been over optimising these case studies (especially with keyword anchor text linking back to the main service page!) and suffered from keywords canibilization in a big way. The net result is that the case studies page are being shown in the search results and the main service page is nowhere.

- After some initial "de optimising" of each case study, should I add each one with a canonical link back to the main service page? I don't want to add a 301 as I actually want people to view these case studies when my client manually gives them the URL, but I want the main services page to show if anyone is searching for this specific service and NOT a random case study.

- When adding a case study in the first instance I am now scared of overoptimising. I genuinely need to repeat each phrase throughout the case study, but what do I do with the URL? Do I miss the keyword out entirely (otherwise there will be 50 case studies all with the same focus keyword). How do I link back to the main service page without using the keyword in the anchor link? Something like "View more about our SERVICE NAME KEYWORD here" and add the link to the word "here" instead of the word "SERVICE NAME KEYWORD"?