This is an interesting question. I'll offer you my opinion on the matter.
The reason why you feel like a glorified medical student is that you are one! That is not to say you area fraud. There is no measurable difference between a late 4th-year medical student and an early 1st year interns in terms of knowledge. If anything, I have seen people argue that sometimes the 4th year might actually have a bit of an edge for having some knowledge from the steps and studying and all that which have eroded somewhat during the very last part of the 4th year and early internship.
Now, what you are describing is a little bit different, you are comparing yourself with interns that have been having 4 months+ of practice and as it might seem silly but those first couples of months make all the difference in building up confidence, getting used to what are the common things to answer or even how certain attendings ask questions and like the answered.
I think by far the most important thing is that you show up interest, willingness to learn and maintain professionalism. Confidence will come as you learn and you will learn and catch up with them.
As for resources, there are plenty. Stuff like Uworld (for boards) or MKSAP can definitely help you a lot for the "questions" and situations but thats probably an investment that will not pay off for you as they won't do much for your actual boards so unless you really think you are way behind in base knowledge at the edge of failure and are willing to spend $$$ to save your neck/reputation this is probably not the most optimal thing to do. That being said, chances are some of the other interns have one of these and you can always ask them to do questions together during downtime or "something".
There is always uptodate. I think it should be standard to always read the whole article that uptodate has for whatever diagnosis you are considering or already made at the start, and then every so often.
My program had a 4 patient cap for interns during call day, call would last ~ 6 hours so that would leave us at least 1:30 per patient. 15-20mins to do Interviews. 5-10 mins to do a focussed exam and 10 mins to put initial orders would still leave you with close to 1 hour to read on your patient, write the note and put an order you decided is appropriate based on your initial read. Then when you go home, 30mins prior to sleep you can read 1 landmark study on the topic for the next day. Once you have done this 2-3 times for the top 10 admitting diagnosis to your institution (CHF, Pneumonia, Alcoholic, Septic-UTI, Kidney stone, HTN Urgency/emergency, DKA, COPD exacerbation, etc) you don't need to read the same article again for a while and it saves you so much time for the next similar admission. My first "simple DKA" took me like 2h+ to set up, examine patient and place orders, now I usually have everything done within 30-40mins with the vast majority of the time being employed actually talking to the patient and the patient's family explaining why this happens and how to avoid it and less than 10mins total to put orders/notes.
Finally, as per electrolyte, fluid management, etc... this is kind of "automatic" work that you get with practice. There is no shortcut for practice. If you have even minimal interest you'd be able to start replacing electrolytes without difficulties within 1-2 weeks of practice as long as you pay attention to what your colleges are doing, show some interest and double-check your work. For an intern, NS is always the answer (LR if you are surg intern) unless sodium is really high in which case free water flushes or D5 is the answer.
