First of all, I think we can know reality to a degree that is useful.
Your definition of truth does not allow you to make that judgement. You could never be sure that your knowledge is of things as they are, or whether your knowledge is merely sufficiently pragmatical i.e. that it works adequately in regard to survival. I think you need to further analyze the meanings you attach to the terms you are using.
I do not however believe we can truly know reality completely.
The idea of “knowing reality completely” is ambiguous. For instance, I may assert that we know reality as it truly is, but that our knowledge of it is far from complete. For example, I can know an acorn as it truly is, plus 10, 000 facts about it. Yet, what is potentially knowable about the acorn is infinite. It’s intelligibility is infinite. So, there is a world of difference between not knowing “reality completely”, and knowing a myriad of things about it truly and not just pragmatically.
And no it does not mean that truth is subjective. The truth in the ultimate sense is objective, but our perception is subjective and thus clouds our view of the truth.
Here is where you confuse truth with the object of knowledge. Truth is not the
things in nature, and so on, that exist independently and externally of our minds. Truth exists in the intellect.
As for science, science is ultimately taken on faith. All of science is essentially based on the notion that our sensory perception gives us truth, and there is frankly no real reason to believe that is correct. Isn’t it quite possible that are sensory organs are there simply to provide us with utility for survival, and have nothing to do with what is ultimately true?
The physical senses give us knowledge of the world. It is a first order level of knowledge. To doubt the reliability of sense knowledge leads to
solipsism. So, you are actually implying a relativity, which when followed to its logical conclusion leaves you in a solipsistic world
If the senses are merely adequate for survival, then you would not be able to know that that is the case, or that it is true, because you would not have a reference point from which to make that judgement. On the other hand, things as known, are the reference point, but you have eliminated that possibility at the outset of your statement and by what meaning you attach to “truth”.
Sense knowledge is a given. But it is merely a knowledge of the phenomenal aspects of things. All knowledge begins with sense perception, but it does not end there, as John Locke says, “Percepts without concepts are blind.”
And once again, I did not say truth is relative. Peoples view of the truth is relative. Obviously this means some people will be closer to the truth than others, but such is life.
It is
true 
that you did not explicitly state “that truth is relative”, but your statement leads necessarily to that conclusion.
And a question I can ask is, what criteria do you use to determine that knowledge is objective? Do you use reason to judge reason? How can use a criteria to judge itself? Doesn’t it ultimately come down to reason seemingly working pretty well for our human purposes? But what does that have to do with real, ultimate, objective truth?
Reason works pretty well as you say, but that is because reason can know things as they are. Things that we know (in the act of knowing) exist in the mind with an intentional and non-physical existence. When there is an adequation between the mind and the thing, we possess truth. Reason also judges. It judges that this or that is true or false. It affirms and it denies. It joins and it separates. Reason judges sense perception as when a stick in the water appears crooked. The mind judges that the stick is actually straight and the eyes are perceiving the water’s distorting effects of the light rays.