Probably not. I am a little confused as to why you would be recieving your ex's pension as well as alimony, but lets say you are. When you add in the required up-front mortgage insurance on a 300,000 purchase price, your gross loan amount will be around $294,566 considering 3.5% down. This will result in a principal and interest payment of about $1,575. this is already pushing 48% debt to income which is beyond standard FHA parameters and does not include: taxes, homeowners/flood/wind insurances, monthly mortgage insurance, or any of the libilities which will show up on your credit report.
If your parents have sufficient income, you can use them as non-occupying co-borrowers, but you need to be realistic as to how you are going to make the payments.