I'll toss my two cents briefly before others chime in:
You are an LCSW practicing independently with a client load of 8 with hopes of expanding I'm assuming.
Unless you want to do more evaluations/assessment oriented things or intend on leaving private practice, I don't really see the point of closing down your practice for 3+ years just to do more schooling.
If you wanted more teaching, you could go to seminars, enroll in CE things, trainings, certifications, etc.
Private practice itself, as you probably know, is all about your marketing, networking, and setting yourself apart. There's many ways to do that than from the potential gain that comes from losing 3+ years of income.
a little wordy because end of semester old fashioned but to summarize:
1. If you want to do more therapy, invest more time/money into yourself and your private practice than into a PsyD.
2. Credentials can be bou- I mean earned through certifications/trainings and all that.
3. Market and Network yourself better to make yourself stand out.