Resentment building over house work

I(f35) have stayed with my partner (m42) for the past 4years. He has a son(M17) and I have a daughter (f11)

SS mom got critically ill and SS had to come stay with us, which was part of the plan anyway to have both kids live with us once we found a suitable home. It’s been a month since SS moved in and we are all doing our best to be mindful of each other. The issue is chores. Initially SS was supposed to do dishes and take the trash out. I then asked him to sweep and mop kitchen twice. Then I asked my partner if we could increase the chores so that I’m not overwhelmed but doing everything as I cook breakfast and dinner 80% of the time. Come the weekend I have very little motivation to do either.

Partner agreed to increase SS chores. So I asked him to clean his room bathroom and stair case, i would clean kitchen/fridge, main bedroom and living room plus laundry. It was my partners turn to cook and he asked me to chop onions and tomatoes for him which I got annoyed by since I spent the day cleaning and him chilling. I suggested he ask SS because he was chilling in his room. Partner then said I’m putting too much on ‘his’ kid and that his kid didn’t come here to work insinuating that I am treating him like a work horse.

He then compared how I treat my daughter when it comes to chores. The last time she visited for a long time she was 9. So I explained how I cannot put the same chores for a 9yr and 17yr, and that now that she is older I treat her the same way. I am hurt that he used the words “my kid’ is not here to work because I treat his son as if he where my own. I try my best to make him feel at home by getting him all his favourite food, buying him clothes etc. I got emotional and told my partner things would be very awkward now as I wouldn’t know how to ask SS to do anything around the house. I then asked him that if he feels SS is too young for chores like cleaning the bathroom and mopping then he must help. He then told me he wouldn’t help clean and that I must find a mop boy. I’m so annoyed that he doesn’t understand how overwhelming cleaning up after two grown people is. I’m hurt at the comparison he made about how I treat our kids because it’s not accurate. Am I wrong for asking SS to help out a little around the house since his dad won’t?