You can get MAX and MIN values from t2 with the following query:
SELECT
t1.name,
t1.value,
(SELECT min(value) FROM table2 t2 WHERE t2.name = t1.name),
(SELECT MAX(value) FROM table2 t2 WHERE t2.name = t1.name)
FROM table1 t1
EDIT: To get the values closer to the t1.value and corresponding y value you could do:
SELECT
t1.NAME,
t1.value,
(SELECT MAX(t2.value)
FROM table2 t2
WHERE t2.NAME = t1.NAME AND t2.value < t1.value) AS maxmin,
(SELECT MIN(t2.value)
FROM table2 t2
WHERE t2.NAME = t1.NAME AND t2.value > t1.value) AS minmax,
(SELECT t2.y
FROM table2 t2
WHERE t2.NAME = t1.NAME AND t2.value = (
SELECT MAX(t3.value)
FROM table2 t3
WHERE t3.NAME = t1.NAME AND t3.value < t1.value
)) AS ymaxmin,
(SELECT t2.y
FROM table2 t2
WHERE t2.NAME = t1.NAME AND t2.value = (
SELECT MIN(t3.value)
FROM table2 t3
WHERE t3.NAME = t1.NAME AND t3.value > t1.value
)) AS yminmax
FROM table1 t1
see it in this fiddle