You have asked lot of questions which need to be addressed separately on the basis of the nature of the question;
If the registered release deed was not signed by yor mother with regard to relinquishment her share in the property which was on your father's name, then she is entitled to her legitimate share in it.
The deed you mention as well wisher deed is not legally enforceable because it was executed out of love and affection without attaching any legal importance to it, especially by not registering this agreement, it becomes a void contract hence she cannot claim any relief out of the deed.
If she is intentionally claiming maintenance from you alone, then you can challenge her claim and can object to her claim for a malafide intention especially while leaving out out her other children in her maintenance petition.
If she cannot justify her stand for not impleading her other children ion this maintenance petition filed agaisnt you then it may also not be maintainable for the reason that she is playing fraud in court especially when you prove that yo have made provisions for her maintenance through the rental income to an extent of Rs. 7000/- per month.
The settlement deed she is reported to have made in favor of her another son may draw a flak however you may have to prove that she is not the absolute owner with clear and marketable title to the property transferred through said settlement deed, hence ascertain the facts From your contents it appears that the proeprty was registered on yor mother's name, hence she becomes the absolute owner of the property registered on her name. Therefore any suit for cancellation of the settlement deed either by your siblings or a suit filed by your wife claiming your son's share in it would be maintainable. In fact since this is not ancestral proeprty, your son is not entitled to any share in the property for whatever the reason he may claim now, not as a right as per law, especially when his father is alive and he had already got his legitimate share from his deceased father's share in the property.
In a criminal case filed agaisnt you it is mandatory that yo have to attend each and every hearing without fail and if not possible you may inform the advocate to file a petition before the concerned court to condone your absence for the reasons stated therein.