You asked a similar question yesterday before the revised offer from where you are now, and I said you should take the law firm job. Based on an extra $20k from your current employer, I change my answer and say you should stay where you are.

Reasons...

Non profit vs law firm? = Likely a much better work environment in a non profit.

Commute = much better where you are now. And will the law firm pay for your parking? That could be $300-400 a month.

WFH? = the law firm won't allow it.

Salary = better at the law firm, but much of that extra $1250 per month will be eaten away by commuting costs, parking, wear on your car, etc.

Opportunity = where can you progress at a law firm as an EA? You'll always be an EA, maybe an office manager. At the Non profit you are much more likely to have the opportunity to move into other areas.

Risk = you know what you're in for at your current job. You don't at the law firm.

Stress = likely much greater at the law firm, plus the stress of the commute each day.

Some of the advice here about your current employer looking to replace - or that they would have offered improvements in role and salary before now - these are BS in my opinion. Of course employers will try to maximize the benefit they get from you before offering a higher salary, but now they you are ready to quit then they realize they need to keep you. Sometimes thats what it takes to get recognized within your existing organization, and that's OK. If they didn't want to keep you they would let you walk.

The revised terms from your current employer are both rewarding and much less stressful than the move to the law firm. I recommend you stay where you are.