Re your Callendar Estate route – have you tried the ‘link trail’ in from the Wood Chip plant? Comes in from the West half way round the Blue…Short but a better way to link in that Forest Road bash you’re doing out to the West.
Also, you can continue East along the farm track (above the top of the Red / along past the Transmitter Aerials) to the mtb trails at Lionthorne (aka Glen Village) these in turn can be linked through to Callendar Park.
You could also bash East along the canal to Muiravonside CP & pick up the Avon Heritage Trail. The AHT from the Aquaduct to Linlithgow Bridge is a peach. There’s some R.O.W’s that will take you back from there (after a wee bit of road) to the canal @ the old brickworks @ Whitecross.
Alternatively you can come off the Lionthorne stuff and link through a strip of woodland @ Mavisbank (due South) to Shieldhill & California by road then turn East just above Blackbraes. That gives you around 5km off road thro the back of Maddieston to the canal. Beecraigs should be doable for you using that link and the canal as an out and back – but only when it’s been bone dry.
Would take too long to give you detailed GR’S for all this – take a map and explore.