This is a fun topic. A lot of deception here, right?
Jacob in a way guaranteed the blessing would be his, not only by deceiving his father, but also because Esau traded his birthright for a serving of stew. Esau also didn't have full appreciation for his birthright.
"...When Jacob had cooked stew, Esau came in from the field and he was famished; and Esau said to Jacob, 'Please let me have a swallow of that red stuff there, for I am famished.' Therefore his name was called Edom. But Jacob said, 'First sell me your birthright.' Esau said, 'Behold, I am about to die; so of what use then is the birthright to me?' And Jacob said, 'First swear to me"; so he swore to him, and sold his birthright to Jacob. Then Jacob gave Esau bread and lentil stew; and he ate and drank, and rose and went on his way. Thus Esau despised his birthright." (Genesis 25:29-34).
Birthrights such as this belonged to the first born. This was a blessing to lead his people and a blessing from God as well. Birthrights also usually guaranteed a generous inheritance. Jacob wanted to guarantee that birthright was his and his mother was even in on it. Isaac was poor of eyesight and ecen though he questioned this a few times, he ended of blessing Jacob.
Genesis 27:27-29 tells that blessing from Isaac:
27 He went over and gave him a kiss. When Isaac smelled his clothes, he blessed him and said,
“The smell of my son
is like the smell of open country
that the Lord has blessed.
28 May God give you dew from the sky,
fertile fields on the earth,
and plenty of fresh grain and new wine.
29 May nations serve you.
May people bow down to you.
Be the master of your brothers,
and may the sons of your mother bow down to you.
May those who curse you be cursed.
May those who bless you be blessed.”
We also see what he said to Esau when he found out in Genesis 27:38-40 :
38 Esau asked, “Do you have only one blessing, Father? Bless me too, Father!” And Esau sobbed loudly.
39 His father Isaac answered him,
“The place where you live will lack the fertile fields of the earth
and the dew from the sky above.
40 You will use your sword to live,
and you will serve your brother.
But eventually you will gain your freedom
and break his yoke off your neck.”
Yes, only God can fulfill the blessings that Isaac had given to Jacob. As you can see, much was taken from Esau and he would have to work harder and serve hia brother. His birthright was taken, but Esau before also gave it away and didn't appreciate it. We all have a spiritual inheritance in Heaven one day waiting for us and it shows us here how Esau mishandled and didn't appreciate his physical inheritance and hoe devastating that was. How much more devastating would it be to lose our spiritual inheritance? To me this shows us to be grateful with what we have and to be wise with what God entrusts us with. I hope this answers some of your questions.