First, no nonsense self defence would be a good place for you to visit and read. It has many good advise on keeping safe, most of them are easy to learn and apply. Some require a little preparation, thought, and understanding.
Second, Rule 1: cardio will get you much further than you think. It is really hard to fight if one is running faster and longer than their attackers. Instead of wasting time learning a new martial art, start running. If you have nothing in your wallet/purse that you cannot replace within 24 hours, drop it and run. If not, remove all items that you cannot replace within 24 hours: none of them belong in your wallet/purse.
Finally, do look up statistics about muggings and assaults where you are. Those are freely available from your LEO and/or city hall and/or national databases. You will probably find that your chances of getting attacked are much less than you think. The Crime calculator: Find your personal risk of being a victim for example.
No martial art will protect you against all weapons and eventuality and anyone telling you different is selling something.
But martial arts help, right? … Yes, they do by giving you more confidence (thus reducing your risk of being pick out as a valid target) and give you some understanding of what it is to be in a fight -- if you ever spare. You already are a third dan (so you know, can do, and understand the basics) and any other art is unlikely to help much beyond that. you already have that card in your deck. Adding Aikido or Krav Maga or BullshitDo is not going to give you more.
You fight like you train. If you want to survive street violence, you are going to have to face it -- even if only in lots and lots of training situations. Look at the statistics you found above and ask yourself if this is a good way to spend your time?
Before choosing an art, chose a teacher. I have seen Aikido dojo that train in mythical manure and some that train active police and army. Same style, utterly different training regimes. The same is true of any art whatsoever: teacher comes first.
Carrying a knife…
⚠ I am not a lawyer, nor do I play one on TV and this is not legal advise!
That said, carrying a knife to use as a weapon in self defence is unlikely to help in any way, shape, or form:
- A knife will always escalate the situation, not diffuse it.
- Any fighting which occurs afterwards will result in potentially fatal injuries. This could lead to either civil or criminal prosecution where you will be the accused, potentially answering murder with premeditation charges.
- Whatever happens, LEO will not be amused at you carrying a lethal weapon and may well shoot you just in case.
More details here.
Anecdote time: I always remember (source) the words of a guy arrested for fatally stabbing his brother in law over a crab stick:
All he had to do was back down… All he had to do was back down…