I have a serious tech lead over him (tanks vs cavalry), but he outnumbers my forces 4 to 1.
i'd have known for certain you were talking about Monty just from that line even if you'd not said it
basically, remember that this is monty and that he's psycho. he fights, especially in the modern era, purely through strength of will and quantity of troops.
bombers are great for offense. they can get city defenses down, and damage stacks, from a distance, and can keep up with your tanks (unlike artillery). you can build new ones and they can fly to the front lines in a single turn, yay! and since he's that far behind tech-wise, you don't even have to worry about fighters.
i like InvisibleStalke's advice, especially about the pillaging. bring the fight to monty, and hopefully he won't be able to send his endless troops to tear up your towns.
in the "file for future reference" category:
chances are that you don't, but if you happen for some odd reason to have any out-of-date mounted units still around that have medic promotions, upgrade them to gunships. medic choppers are terrific, since they can move so far to change stacks/cities they're supporting if necessary. but gunships can't get the medic promotion, so it has to come from an upgraded veteran. tanks can't get medic either, so having a medic with them is really handy. i always always keep around several medic mounties for this purpose but you're not used to late game wars so you didn't know. 9 games out of 10 i use my first great general to earn chariot medic 3, and he stays a chariot (so that he doesn't ever defend the stack) until the days of cavalry are over. he's useful no matter how long the game lasts, and if it lasts that long, he gets to grow up to be a MASH helicopter.