It's possible, especially if it's an AT rich product. However, 500 bp is a rather large product for qPCR. But if your primer efficiencies are 95%-105%, then you're just fine.

Yes it is possible, the Tm depends on the GC content, salt concentration, oligonucleotide concentration, addition of DMSO. You can use IDT DNA OligoAnalyzer for calculation of Tm and also you can use uMelt to simulate your melt curve.

dear Katie & Novanil

Thank you for your recommendations.