Not sure if a postdoc is for me. Terrible at quantitative methods
First of all, happy to hear you're doing better. Many people go through times in their academic career where they feel like utter frauds, it's unfortunately common. 

To your question - I think the key point here is to be absolutely honest with any potential employer. Tell them your strengths and weaknesses and they will make the call on whether you will be a valuable addition to their group. If you tell someone that you would not be comfortable running quantitative analysis and rather focus on something else, and they take you, it would be unreasonable of them to later demand that you run quantitative analysis.

Similarly, if someone is willing to take you under the requirement that you learn these skills on the fly, you need to make a very honest assessment of your own capability to do so. If you can - go for it; if you feel like it'll be too much, politely decline and let them know that you're probably not the best fit for the position. 

Good luck!