Hi there

It's great that you know what you like to do - and actually, it sounds to me like you do know already who you want to work with and what you want to offer those clients...it's just a matter now of deciding that's where you're going to focus your marketing efforts and going for it.
Honestly, I think once you start interacting with these markets you've mentioned you'll find yourself naturally discovering other avenues that you might be interested in marketing to.
Your strengths as a jack of all trades will benefit any client population you decide to work with - and as a business owner you get to decide just what services you'll offer in relation to those strengths. Small biz clients always need web work and admin services, I offer the same hodge podge of services and it works really well for me and for my clients.
It really does sound to me as if the question isn't so much about which markets/which strengths but about which direction to take your marketing and how to get that going - how to reach those clients and sell those strengths - but if I'm missing something please let me know!