Wow, one of the best games here!
Very nice game, graphics are sound, the music is great and very fitting, and the whole game reeks of professionalism. I've devised my own strategy for this game, but as of yet I haven't done the final boss. This strategy should get you there with 9 lives, hopefully intact. :-)
Normal enemies - Shoot them from a long way off, or if there's many, jump and shoot downwards. They can't shoot up at you.
If you get a shotgun, it can kill most of the enemies onscreen in a single sweep - jump and shoot downwards, moving along the screen so the explosion hits the enemies.
1. (Start) Kill all the enemies until you have a full energy meter, but don't waste it. Use it once the car comes, jump over the car and then hit D. Charge up your energy again by killing all the bears until you have a full meter. Then go onto the boss.
2. (Boss) I defeated this bad guy by ducking and shooting. Keep firing at him constantly until he gets close enough to swipe at you. Jump before he kills you, but don't touch any of the arrows, just do an upwards jump, and if you time it right you won't lose any life. Use your energy wisely and you should have him down in a few turns.
3. (Telegraph Pole) You'll have to charge up your meter fully before this bit - remember the bears will just keep spawning, so you can charge it up. Run to the pole and make sure you right up against it, then unleash the energy.
4. (Helicopter Boss) This will launch a row of bombs first. Stay to the left, jump over the first bomb and then start blasting him with your guns, following it over to the right if you dare. Get over to the right side and then follow the helicopter over to the left side, dodging the lasers. Then get over to the right side when the helicopter comes back. Now you should have filled up your energy bar - as soon as the boss fires the gun, hit D. This should wipe out the bears and only leave the helicopter with a little bit of health. Finish it when it starts bombing again.
5. (Final Boss PT1) - Dodge the fists, and JUMP as you dodge, otherwise you'll get killed anyway. Keep firing upwards as he charges that energy ball, if you don't time it right then hit D (if fully charged). Rinse and repeat until you've killed it. Get over to the right hand side of the screen to avoid the laser. The rest is up to you (I haven't finished this bit yet, sadly)