Difficult decision to make

So about a month ago my 9 year old dachshund/feist mix started having explosive diarrhea, it was pure liquid. After trying the white rice/chicken/pumpkin diet for a week and reintroducing her food without it getting better we took her to the vet. It wasn't parasites or an infection so our vet gave us some probiotics and pectin with the wr/c/p diet and then weening back to her regular food nothing was getting better so we went back. Turns out her albumin was low so he threw in another test for Addisons (it came back negative) and suggested an ultrasound. Unfortunately she didn't make it to that ultrasound appointment, that night she was vomiting/ had diarrhea, she wasn't getting up to use the bathroom and was very disoriented. I ended up having to take her to the ER. The vet was saying she has protein losing enteropathy but to find out more an ultrasound was needed. So she had to stay for the day, do the ultrasound, X-ray, and vitals, etc. Which cost us $2,300. After the ultrasound didn't show cancer but there was thickening of her intentestines, she suggested putting her under and doing a biopsy which we couldn't afford. It would have ran us $4-$6k, so we decided to do maintenance at home with meds and a new diet. She was put on dex injection for 4 days then move to Prednisone pills, atopica, paxil, and cerenia for nausea. The new food was hills low fat wet food (which for a month would have ran us $225 a month). We were also given an appointment with an internist for the following Monday.

Unfortunately, she did not do well on this new food with the meds. She was having diarrhea hourly and it was almost completely blood. We took her home last Wednesday and by Sunday she was back at the ER it got so bad (all they did was give her fluids and antibiotics and told us to wait until her internist appt). And on Sunday I started her back on the chicken and rice too curb the diarrhea a little bit which didn't really help. After seeing the internist on Monday she did bloodwork again and suggested a couple of tweaks to the meds (lowered the atopica, and went back to shots of dex for a bit instead of the Prednisone pills). This vet appt cost $500 including the cost of the meds and she said I'm supposed to see her/get new meds weekly. It is now Wednesday and she is still having diarrhea multiple times a day that are almost completely blood even on the chicken and rice. She is also losing weight fast, she went from 29.5 when we first went to the vet for this to 23.8 as of Monday.

I love my dog so much, she is the first pet of my own but I realistically cannot afford this treatment. We are already $5k in the hole from this and I don't see an end in sight (besides her albumin going up a little bit from last Wednesday). I'm not sure what to do and I'm very upset I'm forced to make this decision. From looking online and asking the vet, dogs with PLE have a life expectancy of 6-12 months. Do I go into debt over this? What would you do in this situation? I feel like a horrible owner for not being able to afford this. Any advice/experience/help would be greatly appreciated!