Advice appreciated, maint pending suit and SMaint

Any advice gratefully recieved, just wondering if my solicitor is being too assertive / aggresive re maintenace pending suit and spousal maintenance ?
My wife left around 4 months ago now leaving me in FMHome with 14yo and 17yo(at college) .
Wife is cohabiting in rented flat with new partner, he is working she isn't and hasn't been for many years , shes 44, admiting adultery and cohabitation, at the moment ok with me being main carer.
I'm working full time earning a good salary.
Her solicitor initially requested maintenace of £350/m, my solicitor agreed to this as an interim, to be reviewed after several months, now after 4 months has advised her this will stop soon , ie after around 5-6 months. Wife and sol's response is they now want to go to court to claim maintenance pending suit in addition to anciliary relief.
Solicitor has since learnt I earn reasonable salary and is also suggesting now that around 650/m is a reasonable figure.
Question is , should I go along with my solicitors advice, ie cut it off after around 6m and let her progress through court? As I earn reasonable wage is she likely to get more through the court than I'm presently paying, I don't think there are firm calculations like in CMaintenace so how does court decide, eg is it a%age of net salary ? Is it better for me to be ammicable as possible over this and agree to continue existing payments rather than go to court, I'm not really thinking of the immediate financial situation, rather the longer term if ancilliary relief goes all the way through court etc is there a danger of me being seen as being un cooperative, obstructive etc and trying to get out of these payments?
Can it somehow go against me or is my solicitors approach normal and acceptable in these circumstances?
Any advice is very much appreciated

mine left 12 months ago, adultery and co habiting, no mortgage or rent to pay, her fulltime him full time i have not received a penny off her, my sol said there is nothing i can do if she says she cant pay, me p/time with two children 20 working and 17 full time education, after living expenses i am minus £14 a month so i have to cut back on everything i can, luckily the visa company is accepting £10 a month or i would be minus £200, i will be looking in interest as i have been told i cant get a penny off her until divorce as started but she keeps stalling in signing the paperwork