Okay. So you need to look at your conditions and then find the corresponding VA disability conditions that you believe cause you to not do your job. See what your symptoms are and where that puts you regarding ratings. You are over halfway to getting a pension and now everything will hinge on the % of disability given by the Army. The Army determines what conditions are unfitting and count towards the ratings totals. The VA rates those conditions. The total if more than one condition is VA math. So for example if you had 2 conditions with 30% then the total DOD% would be 50% not 60%.
It sounds like you should have ratings for your back, leg and Radiculopathy. That would be 3 unfitting conditions. Once you have done your homework you want to make sure all of your medical is lined up. The reason for this is you will have a VA C&P exam as part of the process. You need to make sure to mention the symptoms from the C&P that correspond with your ratings. So getting a C&P sheet for each condition will help you to see what it looks like and to make sure you hit all the points.
Then be ready for the NARSUM which is the narrative summary of all of your health conditions. They will state whether the Army docs believe the condition (s) is unfitting or not. If anything isn't listed as unfitting or the information is incorrect you need to be prepared to do a rebuttal and or IMR (Independent Medical Review). The PEB will likely agree with whatever the NARSUM states and those results will be displayed on your DA199.
Then after that you will get a DA199 with the informal decision. If you accept you are locked in and the results are final assuming they find all of the condition static and not likely to change. If the condition is unstable they may put one or more of them on TDRL and you would have a rating but it could change in the future over a period of 3 years. Your conditions will probably be static though you never know.
From there if anything is wrong you can appeal. If a condition should be combat related or if a condition isn't unfitting but should be then you would request a FPEB (Formal Appeal for the PEB). For the Army your attorney can submit a written appeal in advance the FPEB hearing and the FPEB can decide to agree with you and make the changes without having the hearing or they will give some feedback which will help you to know where your case is weak and to prepare to shore up those areas before the hearing.
At the same time of requesting a FPEB you can request a VARR. This is when you challenge the rating that the VA did for an unfitting condition. This be done alone or in conjunction with FPEB. For example say everything is correct on what is unfitting but you think you should be 30% and the VA rated that condition as 10%. The VARR is the submission to try to get that changed. The FPEB can't change ratings for conditions so appealing via a FPEB would not help you.
You will have an assigned PEBLO which will be a paper pusher. They are not knowledgable about the process as a whole or how different results can have life altering outcomes afterwards so DO NOT TAKE THEIR ADVICE as they are not your representative. They just process the paperwork and move your case along until you get out or are found fit for duty. You will get free assigned legal from JAG. They are very knowledgable but they are overworked similar to a public defender. They may only be able to talk to you a day or 2 before your hearing. They have dozens of clients all with tight deadline so they can not provide a lot of time on your case. Everything is hurry up and wait. You wait weeks or months then you get a document like the NARSUM or IPEB and then all of the sudden you have to respond within 7 business days. That is very stressful.
My final advice. Hire a dedicated private attorney. This will ensure the best outcome and if you hire one from the start they can help you shape your case to get the best result. On top of that you have a resource to help you to be proactive and work on medical or any other documentation needed so that when an appeal happens you have what you need. Then your attorney will do all the work on the appeal to then give to your PEBLO. Side benefit that can't be understated: There is way less stress! The whole process is very stressful and you have a lot on the line. There are more cases than I can count where 2 Soldiers had similar circumstance with very different outcomes. DON'T TRUST THE PROCESS. Those who Hire professional representation that specializes only in IDES have a huge advantage. You need to stay the course to ensure you get all that you deserve. Most Soldiers that get poor results just accept them because they are tire of fighting the system and just want to get out. My wife stayed in an extra 6 months while her attorney appealed at every turn to include a FPEB and a VARR but now that she is medically retired with tax exempt income due to the combat related designation and having maxed out her chapter 61 pension. It was worth it. Most likely your medical issues will still be there when you get out so things like health care from Tricare and compensation are a huge help while navigating through the transition from being a Soldier to a civilian. For some reason I thought my wife would get better with more options and freedom after she medically retired but that wasn't the case. She still suffers but with her medical retirement and SSDI we don't have to worry about health insurance or finances as much.