You currently have no company. You have a product. Customers don't care about kLOC, they care about features, stability, and ease of use.

You need to have a 50-50 equity stake with the person you bring on. The product you build, if they think it is saleable, should be part of a payback setup or equity share, or should be licensed to a new entity you create.

My suggestion would be a 1/3rd 2/3rd rev split until you make 1.5mm lifetime rev, and then after that 50/50. You will be paid back for the time you have put in, and you will have a partner who is on equal footing to you. If you need to be 51/49, so be it. If you need to maintain the license to the code, figure that piece out, but you will be best served with a 50/50 split in the long run.