Medical answer: Prostate pathology spreads via the pelvic lymphatic drainage pathways. The main route of drainage from the prostate gland is the lateral route, for which the sentinel nodes are the obturator nodes. From there, the tumor may spread to the middle and lateral chains of the external iliac nodes. The second most common route of drainage is the internal iliac (hypogastric) route, via the lymph nodes positioned along the visceral branches of the internal iliac (hypogastric) vessels. For this route, the sentinel nodes are the junctional nodes located at the junction of the internal and external iliac vessels.
Laymen's answer: It is highly unlikely your prostatitis in the pelvis is the cause of a lymph node in your neck. However, you should still get examined by a doctor. You may have underlying infection, inflammation, and/or cancer in your neck.
I have to think the likelihood of Prostatitis causing pain in a lymph node in your neck is extremely tiny. Also, a radical prostatectomy seems like an extreme measure for prostatitis! I had a radical prostatectomy in Jul 2018 for prostate cancer, and the effects of that are not to be trifled with - 15+ months later, I’m still struggling to regain sexual function & many things are different, including urination. Believe me, you don’t want this unless it’s to save your life, as in if you’re diagnosed w/ cancer. Look up side-effects of radical prostatectomy - I think you’ll agree this is too extreme for prostatitis. There’s a good chance it will lead to permanent ED - some guys regain partial function (w/ help from Viagra, etc.), and a VERY small % regain most of it, but the majority don’t & many are left w/ permanent ED that even Viagra, Cialis, etc. can’t fix. I’m thinking there’s a another reason for your neck pain...
Has a doctor ever checked your neck lymph nodes, or anything about your neck that might be causing that pain?
This says that it can be part of it - https://www.thepelvicpainclinic.co.uk/can-prostatitiscpps-cause-pain-parts-body/ - but you really should get it evaluated to make sure it's not another problem causing your neck pain. I'd hate for you to undergo the prostatectomy and expect every thing else to be better and still have that pain.
Have you seen a CPPS specialist? Google CPPS specialist and your city and state or CPPS specialist US (I'm assuming you're in the US since you mention the surgery isn't covered by insurance).
Try a teaching/university hospital's urology or pain center - they are usually on the cutting edge.