Enriching to 5% has been expectedly very hard because their uranium ore is heavily contaminated with molybdenum, causing constant breakdowns.
From 5% to 20% enrichment is technically much simpler, the moly is largely gone.
The Iranians lack critical quality control and high tech inverters to do any better, any faster.
They are holding at 20% because anything beyond that is legally weaponization and they are not ready for the embargo and possibly military response.
It is technically even much easier to enrich from 20% to 90%. It takes a lead-lined room the size of a garage with the electricity of a refrigerator to produce a bomb a year worth of 90% fuel. It is easy to conceal, virtually no telltale emissions.
The Iranians intend to create as large a stock of 20% as they can, using the threat of weaponization to achieve their goal of regional domination and leadership of Shias in the Muslim world.
HOWEVER, it takes a lot more than fuel to make a bomb. You need "reflectors" like beryllium and a casing of tungsten to get any explosive yield. You need very high energy, low impedance capacitors to set off the high explosive primer. They have virtually none of that and only crude experiments in that area. That will be their "brick wall".
So, after many years they have enough fuel, if enriched to 90%, given an 85% refining efficiency to fuel 1/16th of a bomb.
They might be able to double enrichment production in 2-3 years by bringing more P-1's on line. They say they have P-2's and P-3's but none are online and there are significant technical problems doing so. That is 5-6 years away.
Bottom line, given their existing production, they will have enough 20% fuel for a nuke in 10 years, and from there could enrich enough 90% for a nuke every year.
They may well be able to increase production and it seems likely they could shorten that timetable considerably if they could get their P-2 and P-3's working.
The issue of "reflectors" and casing is very important. For all of Pakistan's supposed 60-80 nukes, they lack that technology and so, have never lit one off. That's right, Pakistan has never tested a nuke. If they do, we will all know how crude their weapons are and they would be a laughing stock like N Korea.
For all the stompin' and snortin', there still is no tested and verifiable "Muslim" nuke.
The outside of the centrifuges are moving at the speed of sound, 80,000 RPM+. That creates a harmonics we can hear. All enrichment gives off radiation of many different kinds, some particles travel through the Earth. Hard to detect, but doable and we are. The Iranians are up front about enrichment levels because they know that we know.
They also learned from Saddam that WMD's are not something to brag about and get yourself attacked.
I think your timetable is optimistic.
After 1945, nobody expected the Russians to make a bomb as fast as they did. Obviously, the Iranians have fewer skilled engineers than Russia did. Mahmoud Ahmadinejad (nee Sabourjian) has an engineering PhD. but his expertise is in civil engineering, not nuclear physics.
Who outside of Varian Semi has the current ability to supply capacitors? Don’t answer this - Varian is known, but I haven’t had a reason to keep current on that technology. Built a drum machine in the 1970s with dual 4004s from Intel plus additional timing from Varian - design oddly looked a lot like Back to the Future tech - fun days, coding a 4004 for more than elevators.
I think it would be several years before any homegrown Iranian tech would be at that level. Israel has the ability, but I’m sure they aren’t sharing. Same for India. Don’t know the details of how Pakistan got there - don’t tell me.
Bomb’em, straife’em, nuke’em!
Might be a language issue. I can barely say molybdenum as a native English speaker. It must be really tough with a (North) Korean accent trying to tell an Iranian "We need to refine out this morynbnmm...moryndddmm....moryydmbn...arr this stuff besides the uranium must go.....I'm so ronery."