I don’t have the writing eloquence of my friend Alan but let me add my two cents.
Alan has responded using arguments stemming out of the field of ethics and moral (which of course I share) but as I understand your concerns are mostly economic. Luckily, as far as migration, moral/ethics and economics lead to the same conclusion: we have to open our doors.
So let me respond by specifically addressing one of your comments which in my view and through the lenses of my economics training is misplaced.
You said “…I’ll go as far as to say that I would not only like to see immigration cease until unemployment is at a more acceptable level…”. Here, I believe you make the common mistake of considering only one side of the labor market. You believe that there is a set number of jobs available and that those jobs if filled by certain people (them) will leave others (us) unemployed. In reality, there is not a certain number of jobs available, the number of jobs available in a society is an output, not an input — it is a result of the individual initiatives of people, of taxes, government policy etc.. Migration is great because it mostly bring young/working age people who have in their overwhelming majority only one desire: make a life for themselves and in doing so, they create growth from which we all benefit.
I came across this video which beautifully illustrates that point.
Welcome those Syrian migrants with open arms, your wallet as well as your heart will be better for it.
Thanks for listening