PDMG is not bad. Probably it can help with fast instrument scan and getting used to them. But I don't think it can relapse FFS. If you can afford some sessions in FFS time to time it will help you to keep up to the standards.
Why do you want to train for FMC unless you have TR? It's not to difficult and never asked or tested for non TR pilots. You need raw flying skills in a jet.
If you want to use MFS additional equipment is necessary.