~$70k sitting in my HYSA; how do I stop hoarding this cash?

27M, living with parents, no debt, no bills; not sure how much cash is too much cash

Looking for some outside perspective on my current setup.

I’m 27, living at home with my parents, currently going to CC for future Nursing program, no debt, and basically no fixed expenses right now. I spend around ~$1k/month on food, going out, dates, etc. Income is roughly $60k–$70k net annually.

Current setup:

• Roth IRA maxed the past 3 years (invested in an index TDF)
• HSA maxed the past 2 years, but funds are still sitting in cash because I live in California and didn’t want to deal with the taxable investing side
• No taxable brokerage account yet

Cash:

• $68k in HYSA
• $2k checking

Roughly mentally allocated as:

• $10k emergency fund
• ~$40k reserved for current/future obligations (nursing school in the next 1–2 years, possible move-out in same time frame)
• ~$6k “fun/self” money

My paycheck currently gets split:

• 50% obligations/savings
• 30% personal spending
• 20% retirement

My Roth IRA + HSA contributions for next year are already being funded as well.

At this point, having nearly $70k sitting in a HYSA feels excessive given how low my expenses are. Since my tax-advantaged space is basically accounted for, I’m assuming the next step is opening a taxable brokerage? 

A few questions:

1. What’s a reasonable amount of liquid cash to keep in a HYSA in my situation?
2. Would you lump sum excess cash into a taxable brokerage or DCA over time?
3. What would you invest in for taxable? Broad index funds? Something else?
4. Any red flags or blind spots with my setup overall?

Appreciate any thoughts/advice.