Hi Ethan, nice little thing!
as usual with pyrenomycetes, a first critical step is to assess whether asci are uni-or bitunicate.
I say critical because it is often not easy to clearly assess.
IKI is not diagnostic but Congo red or coloured inks may be useful to understand the ascus apex anatomy.Judging from your photos the apex is not thickened but appears to be topped by a ring-like structure that would possibly stain in Congo red, heated if necessary.
If positive, this reaction would strongly suggest Sordariomycetes rather than  Dothideomycetes and I suggest you to look into Thyridium, there is a recent paper by Sugita & Tanaka doi: 10.3897/mycokeys.86.78989 which might helpful.

All my best,
Jacques

Hi Ethan,
thanks for your excellent images.They indeed show an apical ring like structure, refractive, unstained in CR but contrasting against the pale red ascus scontent. 
Positive or negative stain in CR is abviously an informative feature, in connection with the chemical nature of  the ring. And it supports the lead toward Thiridium and not toward Dothideomycetes. Apical rings do occur in a few genera (like Delitschia for example) of the latter class but uncorrelated with the other features of your collection.
Good luck!
Jacques

I looked in Barr, Margaret E. 1983. "Muriform Ascospores in Class Ascomycetes." Mycotaxon 18 (1): 149--157. https://doi.org/10.5962/p.417546., where I found a description of Thyridium vestitum. My collection has most of the features mentioned in that description.  The asci in my collection are a bit long. (I will have to check my measurements and the calibration of my 400x). But the yellow, yellow-brown etc. hyphae over the upper parts of the ascomata, the IKI- short-stipitate asci, with a refractive ring. Ascospores that are variable, but basically brown, muriform with 3-5 septa including vertical septa, and 1 oil drop per cell. Narrow paraphyses.  It seems to fit. Thyridium flavostromatum, described in the Sugita & Tanaka also has the yellow tomentum, but much smaller spores and asci and an east Asian distribution.  Of course, there could be more diversity in the genus than documented at the moment, so I will attempt to sequence this collection.

Hi Ethan,
thanks to your efforts, all this sounds good!
Cheers,
Jacques 

After I received my sequence, I was surprised to find that this collection matches Thyridium tiliae CBS 152297 ITS region; from TYPE material 99.79% with 99% query cover.

a good match with a close relative of T. vestitum, this makes sense. Thanks to sequencing, your fungus now has a name. Great!
Cheers, Jacques