Carmina, can you rent your other house? since it is not selling? to lift the burden.
Does your son want a separate birthday party with friends or just a party because you can just do a family party with a couple of friends added. My son hasn't wanted a separate party for the last couple of years so we have a family party. invite the grandparents, aunts etc a pack of dollar store balloons, a dollar store happy birthday banner (been using for years) and a homemade cake from nana and he is happy.
My mil makes cutup cakes where is one sheet cake you cut and rearrange into butterflies, cars etc. She has a couple of books on this that she has used for years. did it for her kids. just a cake mix, frosting and decorations.
for the grandkids she has made a train (I think), a bear, giraffe, butterfly, doll cake. blues clues cake. probably more but I can't remember.