From what I remember from my Byzantine history class, his blinding did not cause much if any backlash domestically or abroad. Tsar Samuel died of a heart attack when he saw the long procession of nearly completely blind men. What helped keep the peace the most was Basil’s fair treatment of the Bulgarians. He allowed the Bulgarians to pay their taxes in kind i.e not requiring it to be paid in gold or silver, and merely demoted the Bulgarian church to an archbishopric.

The number of 15,000 is certainly an exaggeration. Roman field armies at the time varied in size from a few thousand to maybe a max of 30,000 in a single area as a unified force. The Byzantines were very well organized, but to capture and then blind 15,000 would be an astronomical task, as well as a very time consuming one.
The histories were written very much in favour of the Romans so lower numbers of maybe a few thousand are more plausible, but I'd say that only a few hundred would have actually been blinded.
With these lower numbers being likely it would've hardly made an impact on the average Bulgarians view of Byzantium, the enemy is the enemy after all. Basil's policy of issuing taxes in kind (crops, livestock, produce etc) instead of cash helped to ensure that the Bulgarians, who weren't used to paying taxes in coin, would be productive and not angry. He also made sure to marry off Bulgarian nobles to families in Greece and Anatolia and vice versa.
In short, it didn't impact the integration and administration of the newly conquered Bulgarian territories because the number of men blinded has been greatly exaggerated and Basil's practical and popular decisions to not introduce taxation in coin.