Here's some info for you on controlling it--unfortunately it's not something you can really get rid of but it can be managed to some extent. http://www.ces.ncsu.edu/depts/pp/notes/oldnotes/fd3.htm You might also contact your local extension office, they may have some good suggestions for you as well.
However, if you have a large number of plants from the Rosaceae family on your property, your best bet may be to get rid of the infected pear before the fireblight has a chance to spread to other plants. If you really want another pear after that, try looking for a cultivar that's resistant to fireblight. (Rosaceae family includes apples, pears, plums, cherries, almonds, roses, as well as many other things)
I have been working in gardens and on landscapes for awhile. Once you have fireblight the only practical things to do is remove the blighted plant.
It will spread and there is no effective control. Once the bark cracks and those spores are released you are going to have it all over your area. Your yard, the neighbors yard and in every yard for 1/4 mile downwind.
I have roses and cheeries and apples I would really hate to get rid of my 2 pear trees both have fireblight both are just 3 years old I got from FoodLion and BigLots. I did do heading back cuts one year in the summer would me trimming it caused the FireBlight also I transplanted one of them two times. Would me moving it caused FireBlight after mpoving it the blight started. The first year I planted it the fruit was good It has not make fruit since. The second one I planted has not make fruit since I got it. The bark has not crack yet. The reason I would hate to get rid of them is they are so new trees. And I would have to buy 2 new ones because of the pollination issue.
The link I posted above mentions some varieties that are more & less susceptible to fireblight. No tree will be completely immune to it, but the resistant varieties are less likely to get it. Sounds like you've got a lot of other plants in your yard that can get fireblight, so unless those pear trees are more important to you than all the other plants I would seriously consider getting rid of them. Especially since you can't really cure fireblight, your pears may never really be healthy anyway and there's no sense taking a risk with your other plants. Trimming your trees and moving them would not have caused them to get fireblight unless you trimmed them with pruners that you'd trimmed another infected plant with and hadn't sterilized, or if when you moved them you inadvertently moved them closer to some other plant that also has fireblight which would have made it easier for the infection to get transmitted.
Symptoms can vary in severity, so yes you could see it just on the blooms and still have healthy leaves. Over time you may see more and more problems though. As far as why your Kieffer still got it...first of all you mentioned buying your trees at Big Lots and Food Lion so there's a chance it wasn't labeled correctly. And secondly, as I already mentioned even resistant cultivars can still get it, they're just less likely to. But no pear is going to be 100% immune to it. It can also affect ornamental pears just like it can affect the fruiting ones, any pear tree can potentially get it. And it could affect the same parts of the tree as are affected on the fruiting pears--fireblight doesn't know the difference between ornamental and fruiting pears.
If you would take the time to read the link I provided above, it tells you the parts of the tree that can be affected and blossoms and fruits are both on the list as well as the branches. And as I also said before, fireblight can't distinguish between ornamental and fruiting pears, so the symptoms would be similar.
Nothing is going to kill fireblight, all you can hope to do is manage the symptoms but I'll reiterate my advice to consider getting rid of those trees unless you want your apples, etc to become infected too. And I can't imagine your tomato spray will have any effect at all, those sprays are usually meant to help correct calcium deficiency which is a contributing factor in blossom end rot, and I can't imagine that would have any impact at all on fireblight symptoms since it's caused by a bacteria not calcium deficiency.
I found it may not be FireBlight the nursery man said that if the branch tips are not black then its not FireBlight and there not black and he said my problem was a fungus said he could not think of the name at the moment but to use fruit tree spray with sulfer and captain. My friend gave me some he did not use anymore since his trees got old and died it is dragon fruit tree spray which has a fungicide aphicide miticide scalicide so its supposed to treat bugs to and the fungicide should treat any fungus I have even if it is FireBlight. His assasiant said that she once had FireBlight on her apple tree and she put down lime for some Azaleas she had planted under it and the FireBlight was gone the next year and if I remember correctly she said to use potassium or phosphate.