How long after wisdom teeth removal should I wait to eat solid foods & how long can pain last? Still in pain after 4 days. Vicodin just makes sleepy,

When pain decreases. You can eat solids when it is comfortable to do so. Normal to have some pain after 4 days. If the pain has gotten worse recently, it is probably a dry socket and you need to see the treating dentist tor evaluation/treatment.
How are you? How long to wait before resuming to usual diet depends on how fast you heal. Your speed of healing depends on your overall health, nutritional value of your food history, etc. Since you already suffer from chronic inflammatory disease and chronic pain (back) that raises stress hormones in blood, healing may be slow. Focus on nutritious food + fluid intake. Rest well. Get post-extraction exam also.
Individualized. Everyone is different and there are many different extremes of wisdom teeth surgery. All patients should eat something the evening of surgery with the consistancy of the food ranging from pureed to semisolid depending on the extend of your surgery. Whatever you start with you should try to daily increase the your diet but without causing pain or discomfort.