Staff Development -- or Nursing Professional Development (NPD) as it is "officially" called now can be a tricky field to get into as schools of nursing don't usually teach it. Most academic faculty have little or no expertise in that field and they rarely include any related content in the Nursing Education curricula. Many of us get into the field by starting small -- precepting, serving on a unit-level education committee, becoming a unit-based clinical educator, etc. I ended up here by becoming a CNS decades ago and gradually transitioning into staff education. Others find schools that allow their students in Nursing Education to do practicums in NPD with NPD specialists. You seem to have found such a program -- and that's a legitimate route to take.
I am also 58 years old, so I understand your financial concerns. I don't think it is necessary for you to get a DNP to get into staff development
. You could stop investing your time in other ventures and start focusing on unit-level education and probably make the transition -- or seek jobs in staff development at other hospitals with PICU's if you are willing to relocate. You could also start volunteering to teach CPR, PALS, etc. and develop your resume/porfolio in the staff development arena that way. You could alos become active in a professional organization and get involved in their continuing education activities (conference planning, learning modules, etc.) If you were to stop investing your time and energy on so many other things (such as academic education) and start focusing your efforts on transitioning to a staff development role, you could probably do it without a DNP. However, if you have this dream of a specific project and you can financially afford to get the DNP ... and you won't feel fulfilled unless you pursue this dream ... then go for it.
It's a legitimate pathway that would give you some credentials in staff development. Those credentials won't guarantee you a job, but they add to your qualifications. Just as important, it may help you focus on staff develoment (instead of other things) and help you make contacts within the field of Nursing Professional Development that would help you find a job -- or help you set up your own company to "sell" the product/program that you want to create.
Other things I would suggest:
1. Explore ANPD -- That's the Association of Nursing Professional Development. That's the specialty organization for people in nursing staff development. Here is a link to their site. Read their journal to learn more about the field, go to their conference, etc. to learn more and to network with other people in NPD. ANPD - Association for Nursing Professional Development
2. See if there is a local chapter of ANPD in your region. Getting involved with a local or state-wide chapter would help you learn and network.