The conclusion first: he was level 98. I got it wrong.
The original novel never explicitly said he was level 98, but one passage stated that Long Yeyue's realm was higher than his and that she was a Limit Douluo, which meant Han Tianyi had not broken through to Limit Douluo.
The main reason was that his spiritual power was at the peak of the Spirit Domain Realm, close to the Divine Origin Realm. Taken together with another setting-that breaking through to the Spirit Domain Realm allowed someone to break through to Limit Douluo-this led me to think he was level 99.
That setting about being able to break through to Limit Douluo upon reaching the Spirit Domain Realm probably also had a prerequisite: the first two soul cores had to be in the middle and lower dantians.
Nothing for it. Maybe Han Tianyi's spiritual soul core was not his third soul core, and he had condensed a spiritual soul core as his second instead.
I'll change all the earlier references to Han Tianyi being level 99 to level 98, so I needed to let everyone know here. There won't be any major changes; only his level will change a little.