Курсор не реагирует на lineEdit и как вынести _pos из класса MyLabel в класс MyWin?

Пробуйте так:

import sys
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.Qt import *


#from add_label_des import *
class Ui_Form(object):
    def setupUi(self, Form):
        Form.setObjectName("Form")
        Form.resize(691, 385)
        Form.setMinimumSize(QtCore.QSize(691, 385))
        Form.setMaximumSize(QtCore.QSize(691, 385))
        icon = QtGui.QIcon()
        icon.addPixmap(QtGui.QPixmap(":/ico/Python.ico"), QtGui.QIcon.Normal, QtGui.QIcon.Off)
        Form.setWindowIcon(icon)

# !!! MyLabel        
#        self.label = QtWidgets.QLabel(Form)
        self.label = MyLabel(Form)                                  # !!! MyLabel 
        self.label.setGeometry(QtCore.QRect(0, 0, 701, 391))

        self.label.setStyleSheet("border-image: url(im.png);")      #<--- Ваша картинка
        self.label.setText("")
        self.label.setObjectName("label")

        self.lineEdit = QtWidgets.QLineEdit(Form)
        self.lineEdit.setGeometry(QtCore.QRect(450, 274, 241, 21))
        self.lineEdit.setObjectName("lineEdit")
        
        self.lineEdit_2 = QtWidgets.QLineEdit(Form)
        self.lineEdit_2.setGeometry(QtCore.QRect(450, 295, 241, 21))
        self.lineEdit_2.setObjectName("lineEdit_2")
        
        self.lineEdit_3 = QtWidgets.QLineEdit(Form)
        self.lineEdit_3.setGeometry(QtCore.QRect(450, 316, 241, 21))
        self.lineEdit_3.setObjectName("lineEdit_3")
        
        self.lineEdit_4 = QtWidgets.QLineEdit(Form)
        self.lineEdit_4.setGeometry(QtCore.QRect(450, 337, 241, 21))
        self.lineEdit_4.setObjectName("lineEdit_4")
        
        self.pushButton = QtWidgets.QPushButton(Form)
        self.pushButton.setGeometry(QtCore.QRect(470, 360, 75, 23))
        self.pushButton.setStyleSheet("QPushButton {\n"
"                         background-color: #54e346;\n"
"                         }\n"
"                         QPushButton:hover {\n"
"                         background-color: white;\n"
"                         }\n"
"                         QPushButton:pressed {\n"
"                         color: #626AB0;\n"
"                         background-color: #D5D4D4;\n"
"                         }")
        self.pushButton.setObjectName("pushButton")
        self.pushButton_2 = QtWidgets.QPushButton(Form)
        self.pushButton_2.setGeometry(QtCore.QRect(600, 360, 75, 23))
        self.pushButton_2.setStyleSheet("QPushButton {\n"
"                         background-color: #fa7f72;\n"
"                         }\n"
"                         QPushButton:hover {\n"
"                         background-color: white;\n"
"                         }\n"
"                         QPushButton:pressed {\n"
"                         color: #626AB0;\n"
"                         background-color: #D5D4D4;\n"
"                         }")
        self.pushButton_2.setObjectName("pushButton_2")

        self.retranslateUi(Form)
        QtCore.QMetaObject.connectSlotsByName(Form)

    def retranslateUi(self, Form):
        _translate = QtCore.QCoreApplication.translate
        Form.setWindowTitle(_translate("Form", "Form"))
        self.lineEdit.setPlaceholderText(_translate("Form", "Введите ip"))
        self.lineEdit_2.setPlaceholderText(_translate("Form", "Введите организацию"))
        self.lineEdit_3.setPlaceholderText(_translate("Form", "Введите улицу"))
        self.lineEdit_4.setPlaceholderText(_translate("Form", "Введите город"))
        self.pushButton.setText(_translate("Form", "Ok"))
        self.pushButton_2.setText(_translate("Form", "Cancel"))


class MyLabel(QtWidgets.QLabel):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.parent = parent

    def mouseReleaseEvent(self, event):
        if event.button() == Qt.LeftButton and self.parent.flag:
            self._pos = event.pos() # <--- Взять
            print(f'def mouseReleaseEvent(self, event): {event.pos()} <----')
            
            self.parent.label_pos.setText(
                f"<b style='color: #fff'>.</b> x:{self._pos.x()}, y:{self._pos.y()-10}")
            self.parent.label_pos.move(self._pos.x(), self._pos.y()-10)
            self.parent.label_pos.adjustSize()
            self.parent.flag = False
# !!! +++            
            self.parent.coordX = self._pos.x()               # !!! +++           
            self.parent.coordY = self._pos.y()-10            # !!! +++    # ??? -10
            

class MyWin(QtWidgets.QWidget, Ui_Form):
    def __init__(self):
        super().__init__()
        self.setupUi(self)
        
        self.flag = False              
        self.coordX = None                                       # !!! +++                          
        self.coordY = None                                       # !!! +++                
        
#        self.myLabel = MyLabel(self)

#                                                        vvvv
        self.pushMyButton = QtWidgets.QPushButton('Add', self)   # - self.myLabel)
        self.pushMyButton.move(10, 10)
        self.pushMyButton.clicked.connect(self.func_connect)

#                               vvvv        
        self.label_pos = QLabel(self)                            # - (self.myLabel)

#        grid = QtWidgets.QGridLayout(self)                      # - 
#        grid.addWidget(self.myLabel)                            # - 

        self.pushButton.clicked.connect(self.add_new_label)
        #self.pushButton_2.clicked.connect(self.add_new_row)

    def func_connect(self):
        self.flag = True
        # self.pushButton.setEnabled(False)

    def add_new_label(self):
        text = self.lineEdit.text()
        text2 = self.lineEdit_2.text()
        text3 = self.lineEdit_3.text()
        text4 = self.lineEdit_4.text()

#                         vvvvvvvvvvv        
        print(f'coordX = {self.coordX}')               # <----- Получить _pos.x()
        print(f'coordY = {self.coordY}')               # <----- Получить _pos.y()
#                         ^^^^^^^^^^^        
#        self.coordX = None                             
#        self.coordY = None                             

        if text and text2 and text3 and text4:
            print(f"{text}\n{text2}\n{text3}\n{text4}")
        else:
            msg = QMessageBox.information(self, 'Внимание', 'Заполните все поля!')


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    w = MyWin()
    w.show()
    sys.exit(app.exec_())