Hi Mike,
I only got temporary results from Saw Palmetto and over the counter prostate supplements. Like you said, I experienced good and bad voids. The only thing that actually allowed me to go when I was quite restricted was Jack Daniels Whiskey. If I woke up in the middle of the night feeling like I needed to go and couldn't, I'd drink a whiskey and walk around the kitchen for 10 minutes and then I'd be able to go.
900ml is a lot to retain. I'm surprised you didn't feel it. That can be a problem as you can damage your kidneys. A relative of mine has no sensation of needing to urinate and caths every 6 hours around the clock. He had a turp but it only lasted a few years, then was told his bladder had lost elasticity and could no longer contract, so he chose to cath on schedule.
When I went to the emergency in full retention in the middle of the night they removed 1400 ml and I was begging for a cath. After that I bought some hydrophilic (packed in sterile water and pre-lubricated) caths and learned to cath myself.
Having been down this road for more than three years now, I found flomax (or the generic tamsulosin) to give good relief. For me though it stopped working after a few months. It's very difficult in these cases to pinpoint the actual problem.
If I were you I'd have the stones removed with a cystoscope in surgery and start taking the flomax or tamsulosin and see if that works.
In three years I've had the TUMT (microwave procedure to open the prostate), a Greenlight XPS laser to remove 70g. of a 120 g. prostate, a cystoscope procedure to remove a membrane blocking the urethra,
tried self cathing every 2 eeks to "keep the channel open", and emergency cysto surgery to cauterize three bleederrs causing a hematuria, remove bladder stones, and resection (widen) the bladder neck. When I had the Greenlight Laser my uro said he uncover a lot of of pus in my prostate that were never seen or diagnosed with tests as chronic prostatitis. So all contributed to my symptoms, and just widening the prostate alone with the laser turp only lasted 6 months for me.
Regarding the retro, my uro preserved a flap of tissue above the valve that releases semen into the prostate to direct the semen down and out instead of back into the bladder. Most uros don't practice this. Even though he did the laser turp and then the cysto resection and cauterization and bladder stone removal, he said he would try to spare me from retro, and he did, but he said he couldn't guarantee it. Whether the stent would interfere ewith ejaculation is something i don't know. Certainly if it got impacted and had to be removed surgically, it's a possibility the surgeon wouldn't be looking to spare you from retro.