surrender existing chimney for new stand alone flue??

Hello and thanks in advance for any help or insight. Some background...Last year in installed a older Tarm MB 55 and placed it series with my oil burner heating 5K sq. ft. with baseboard hot water and no storage. Worked quite well hooked into an 8" dedicated flue in a 3 flue interior chimney. I was burning what would amount to lousy wood by forum standards last year as I had to buy it and it was on the wet side, but seemed to work well enough....no creosote!! I say this because this year I purchased 8 cords of 2-3 year old seasoned red oak from my neighbor (he was moving to AZ) and I can go into the Creosote business!! I mean, nothing like what I have seen on the forum. If you can get the doors open, the creosote drips down the length of the door and is 1/4' thick where the door meets the frame in both the loading area and the ash clean out. The inside of the whole firebox is slick wet looking black sheen. I managed to completely close over the 8" flue about 8' down from the top of the chimney in one months burning time with creosote. Stove pipe looks similar. The stove pipe is about 4' total length with (2) 90 degree bends and a 45 degree. (see picture), this is single walled. The flue is 8" square masonry with mortar joints infringing on the inside diameter a bit, this is probably pretty common. I check my stove pipe and boiler (clean them) monthly and clean the Chimney twice a winter (don't burn in the spring/summer)

So with no changes this year and "good" wood (no I didn't put a hydrometer on it, but I was a carpenter and have spent a lot of time around wood and this is dry and 3-4" splits), I have this huge change and never ending creosote issue.

What I have tried based on forum reading thus far

1) smaller fires and char wood before closing door completely
2) sealed up any air leaks in the stove pipe fittings and the chimney clean out
3) making sure the ash and logs are away from the lower rear section of the boiler to make sure draft is not obstructed.

No differences noted as a result. Now I know the number of bends in the stove pipe are not ideal and in looking at the forum I'm guessing the likely response is wood is the culprit as it is the only thing that changed from last year. But I was wondering if you thought by moving the the boiler to a separate 8" class A exterior flue with only one 90 degree turn in it, that may get rid of my creosote problem by increasing the draft.

I have not measured the draft (don't know how), but have noticed my stack temps (or stove pipe 6" above the boiler outlet) run consistently about 150-250 degrees unless I open a door or lots of heat is called for then it get up to 400-600 for a short time. People talk about running a hotter fire, but I'm limited by my water temp and frankly the stove just doesn't need to run hot to heat the house, hence I'm hoping this is a draft issue.

Forgive my ignorance on aspects of this.

Thanks,

Bill