I'm sorry that your question wasn't answered in a timely manner. I'll address your concerns as you presented them...
1) I don't understand your vet's reticence in repeating testing which is more likely to be informative when Dolly's stools are abnormal rather than normal.
2) A gastrointestinal diagnostic panel of blood, urine, and fecal tests is the most complete and cost-effective manner of testing Dolly. It should contain a PSL which is most sensitive for detecting the presence of pancreatitis, TLI for detecting exocrine pancreatic insufficiency (EPI/a deficiency in digestive enzymes produced by the pancreas), and serum folate and vitamin B12 assays looking for malabsorption syndromes.
3) If nothing untoward is seen in such testing, an abdominal ultrasound is the next diagnostic of choice. This imaging is the most sensitive and readily available imaging modality for the abdomen and can "see" inflammatory bowel disease (IBD) and its sequela small call lymphoma. Small cell lymphoma rarely will be seen in the peripheral blood as part of a complete blood count (CBC).
4) Her maintaining her weight is a very positive prognostic sign. It's not consistent with lymphoma, EPI, or malasorptive disorders.
5) Thank you for posting her last diagnostics. Chronic renal insufficiency is likely but the very important complete urinalysis is missing to better understand Dolly's kidney health.