Cold Malo is ok if you make sure you are safe. As long as you have active bubbles, the co2 is protecting you. I'm thinking the temperature is an issue as others why it is taking time. Remember, traditionally Malo fermentation happened in the spring as the cellar warmed up.
I try to keep my Malo phase at 60f, if pH is Good<3.8 and I can keep a clean airlock. I try to hit 65 to get it started, then cool it down. It can take 10-12 weeks. There is risk due to holding off on meta, but I like the results of the colder process. I leave it on the second lees as well.
Remember, do nothing, as long as bad stuff isn't happening, is often the best course.