Form 8949 is for disposal of capital assets -- maybe you have sale of stocks, or some kind of property. In some cases, form 8949 can't be e-filed with your return. In that case, you can e-file the rest of your return but you must mail a printed copy of form 8949. Form 8453 is a cover page that allows the IRS to link the mailed form to the rest of your electronic tax return.
For your other question, estimated payments should be on line 65. I'm not sure why they wouldn't be. Did you verify that your estimated payments are recorded properly? Check the Estimated and Other Taxes Paid section of the Deductions and Credits page.