It is easier to use the /users/{id}/top-tags (JSON) endpoint for a single user.
That will give you for a given user all their tags with score and count for question and answers. Don't let the "top" misguide you. The user I used as an example has 440 tags in the API result and that is only 40roughly 50 tags off compared to their site profile (and SEDE). Close enough I would say.
{
"items": [
{
"user_id": 811,
"answer_count": 176,
"answer_score": 10331,
"question_count": 0,
"question_score": 0,
"tag_name": "javascript"
},
{
"user_id": 811,
"answer_count": 37,
"answer_score": 4211,
"question_count": 0,
"question_score": 0,
"tag_name": "html"
},
{
"user_id": 811,
"answer_count": 95,
"answer_score": 4031,
"question_count": 0,
"question_score": 0,
"tag_name": "jquery"
},
Do notice the default filter doesn't include Total in the wrapper, so you have to add that field if you want to know upfront how many pages you have to fetch.