Good advice above about getting independent adult support. Consider telling the family you are grateful to them and as you say love them as your own family, but would consider it disrespectful to Sikhi if you adopted it or any faith to secure stable housing and food on the table.
Are they suggesting you leave the house if you don't adopt Sikhi? As suggested in posts above you should respect basic house rules. Are you able to get in touch with young Sikh sangat for support? You know you have the right Sikh support if they say you should not feel pressured to adopt SikhI.
Reading your post, you are a warrior in life at a young age and you are forced to contemplate the human condition. You obviously have accepted Sikhs as family regardless of your own leanings. Please continue to lean on the wider community, the gurdwara and this forum as you need.
You will always be part of the wider Sikh family. In that sense Greg consider yourself loved and adopted by us, and especially us on this forum regardless of your faith as long as you support truth and humanity. You are our child and our little bro with full and equal privileges of family on this forum.
Study hard and know we're here anytime you wish to reach out.