I was downsized in 1995 after 25 years with a major company. Although I had enough company service to retire, I was not old enough. Now, my former employer is merging with another company. I understand it is my former employer's aim to FORCE all downsized employees to take their pension after they reach age 50. Apparently, they are not planning on offering the pension in a "lump sum," just monthly.

Can my former employer FORCE this upon us??

No.
The involuntary cash-out limit is $3500. Recently the law was changed permitting employers to amend their plans to raise this limit to $5000, but the old limit still applies until the plan is actually amended.
However, there may be something else going on here. I suggest you obtain some more facts (not rumors) and post them here for further advice.