The arm / pivot looks good... not sure if your wheel mounts will take the strain of 4000lbs+ of thrust being applied to a 30lb weight.

It may be desirable to have the chassis flex enough to allow the base to touch the floor .....thus allowing the floor to take a good percentage of the load away from the wheels and mounts.....or perhaps squidgee tyres?

There is also going to be a fair ammount of bending moment applied to the chassis forward of the ram .......it might be a good idea to add a brace of some sort?
You could incorporate your Ali manifold and bottles as structural strength.

Just thoughts ......